immunohistopathologic findings in herpes simplex virus ... virus chorioretinitis in the von szily...

Investigative Ophthalmology & Visual Science, Vol. 33, No. 1, January 1992Copyright © Association for Research in Vision and Ophthalmology

ImmunohistopQthologic Findings in Herpes SimplexVirus Chorioretinitis in the Von Szily ModelMondi M. Zalros,* E. Mirchel Opremcak,t Ramzi Hemady,* and C. Stephen Foster*

After anterior chamber inoculation of herpes simplex virus type 1 (HSV-1), some mice have a charac-teristic pattern of ocular disease, including ipsilateral anterior uveitis, relative sparing of the ipsilateralretina, and necrotizing contralateral chorioretinitis. It was reported previously that susceptibility to thecontralateral chorioretinitis is associated with the Igh-1 locus; congenic mice differing at this locushave different rates of contralateral disease. The immunohistopathologic findings of this model inIgh-1 disparate congenic mice are reported after examining immune cell populations (CD4, CD8, Thy1.2, la, Mac, and immunoglobulin G cells) in both ipsilateral and contralateral eyes and the recruitmentkinetics of these cell types in various ocular tissues. In both HSV-susceptible BALB/c and HSV-resis-tant C.B-17 mice, the ipsilateral eye undergoes early cellular infiltration, and the contralateral retina isdevoid of cells until day 10 postinoculation. In BALB/c mice, a late dramatic rise develops in Mac andla cells in the ipsilateral and contralateral choroid (P < 0.005) compared with C.B-17 mice. The C.B-17mice have an earlier, mild cellular infiltration of the uveal tract in the ipsilateral eye, abrogation of thelate Mac and la cellular recruitment in the ipsilateral choroid, and an absent contralateral response.These strain-specific immunohistopathologic differences help to explain Igh-1-linked HSV retinitispatterns in this model. Invest Ophthalmol Vis Sci 33:68-77,1992

The importance of the host immune response incontrolling ocular herpetic disease is shown by thehigh incidence of herpes keratitis, uveitis, and retinitisin immunosuppressed patients (eg, patients with ac-quired immune deficiency syndrome and transplantrecipients).1"3 The von Szily model of herpes chorio-retinitis affords an opportunity to define the role ofhost immunologic parameters in herpetic retinal in-fection. In this model, inoculation of herpes simplexvirus type 1 (HSV-1) into the anterior chamber (AC)of one eye results in ipsilateral anterior uveitis, rela-tive sparing of the ipsilateral retina, and necrotizingchorioretinitis of the contralateral eye.45 Studies withimmunodeficient mice found that T-cell-mediatedimmune responses probably play a role in the protec-tion of the ipsilateral retina.6 In addition, ipsilateralprotection is lost when the virus is injected into thevitreous cavity rather than into the AC, suggestingthat the route of viral inoculation is important in im-

From the *Hilles Immunology Laboratory, Massachusetts Eyeand Ear Infirmary, Boston, Massachusetts, and the fDepartment ofOphthalmology, Ohio State University, Columbus, Ohio.

Supported by Public Health Service (Bethesda, MD) grants EY06008 and EYO5839, The National Society to Prevent Blindness,Schaumburg, IL, The Heed Foundation, Chicago, IL, and The Su-san Morse Hilles Fund, Boston, Massachusetts.

Submitted for publication: July 8, 1991; accepted August 22,1991.

Reprint requests: C. Stephen Foster, MD, Department of Oph-thalmology, Massachusetts Eye and Ear Infirmary, 243 CharlesStreet, Boston, MA 02114.

munologic priming and the subsequent generation ofipsilateral retinitis.78

A clue to the immunopathogenesis of the contralat-eral chorioretinitis may be the Igh-1 gene locus; con-genic animals disparate at this locus have differentpatterns of contralateral disease.910 These congenicmice are genetically identical except for a limited re-gion of diversity on chromosome 12 in the region en-coding for immunoglobulin heavy chain synthesis(Igh-1)." Because these Igh-1-disparate congenic ani-mals show equivalent permissivity to HSV-1 invarious ocular tissues (retinal pigment epithelial cellsand keratocytes), host permissivity for HSV replica-tion differences cannot account for their variable dis-ease susceptibility patterns.12-13

Some authors believe that the development of con-tralateral retinitis in this model correlates withchanges in systemic immunity they call AC-asso-ciated immune deviation (ACAID).7814-'6 This dis-order is characterized by suppression of delayed-typehypersensitivity (DTH) responses to the injected anti-gen (HSV) with an intact HSV-1 neutralizing anti-body response. However, we recently showed that theIgh-1-congenic animals have equivalent suppressionof DTH after intracameral inoculation.10 Similar ob-servations were reported in various inbred murinestrains with a dissociation between contralateral HSVchorioretinitis and the development of ACAID.17 Wedescribe the immunopathologic characteristics of theipsilateral and contralateral eyes of Igh-1-disparate

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congenic mice after AC injection of HSV into one eyeand analyze the dynamics of cell-type traffic kineticsduring the evolution of the von Szily model.

Materials and Methods

Virus

The HSV-1 (strain KOS) was obtained from Dr.David Knipe (Harvard Medical School, Boston, MA)and passed twice in Vero cells (CCL 81; AmericanType Culture Collection, Rockville, MD). The virusfor all experiments was produced from infected Verocell monolayers as described previously.18

Animals

The BALB/cByJ (Igh-la) breeding pairs were ob-tained from Jackson Laboratories (Bar Harbor, ME).The C.B-17 (Igh-lb) breeding pairs were provided byDr. Charles Sidman (Jackson). All herpes-infectedmice were housed in a VR-1 isolator (Lab Products,Inc., Maywood, NJ) in a professionally staffed animalcare facility. Animals were handled in accordancewith the ARVO Resolution on the Use of Animals inResearch.

Inoculation

The mice were inoculated with 1.5 X 104 plaque-forming units of HSV-1 strain KOS into the ACs oftheir right eyes. The animals were anesthetized withether and topical proparacaine, and the injection wasdone under an operating microscope. Aqueous drain-age through a paracentesis with a glass needle was fol-lowed by injection of 5 pi of the appropriately dilutedvirus into the AC through the beveled coraeal paracen-tesis wound using a 33-gauge needle connected to a50-/il Hamilton (Reno, NV) syringe.

Immunohistopathologic Findings

The eyes were snap frozen and embedded in Tissue-Tek OCT Compound (Miles, Elkhart, IN) immedi-ately after removal. Using an IEC Minotome (Need-ham Heights, MA) cryostat, the eyes were sectionedserially at a thickness of 4 nm. Whole-eye cross-sec-tions were fixed to gelatin-coated 12-well microscopeslides and stored at —70°C until analysis. The slideswere then air dried, fixed for 10 min in acetone, andincubated for 20 min in 1% bovine serum albumin.Then the sections were incubated for 45 min with theprimary antibody at various dilutions. Optimal dilu-tions of the primary antibodies were obtained in ourlaboratory by staining sections of mouse spleen andlymph node with the immunoperoxidase procedure.Primary antibodies and their working dilutions in-cluded: anti-Thy 1.2 (T-lymphocytes) 1:299, anti-

Lyt-1 (CD4, helper/inducer T-lymphocytes) 1:100,and anti-Lyt-2 (CD8, suppressor/cytotoxic T-lym-phocytes) 1:10 (Becton Dickinson, Mountain View,CA); anti-mouse la (antigen-presenting cells) 1:100,and anti-mouse anti-human Mac-1 antigen (macro-phages, natural-killer cells, and polymorphonuclearneutrophils) 1:25 (Hybritech, San Diego, CA); andhorse anti-mouse IgG (Vector, Burlingame CA).

After incubating with the primary antibodies, sec-tions were washed three times with 0.01 M phos-phate-buffered saline (PBS) and blocked for endoge-nous peroxidase using 0.3% H2O2 in PBS for 30 min.Then the sections were incubated with a 1:500 dilu-tion of biotin-conjugated affinity-purified mouseanti-rat IgG (Jackson Immunoresearch, Avondale,PA) for 45 min. After three rinses in PBS, the tissuewas incubated for 45 min with a 1:1000 dilution ofperoxidase-conjugated streptavidin (Jackson Immu-noresearch). The tissue was rinsed in PBS and thenoverlaid with peroxidase substrate containing 3-amino-9-ethyl-carbazole and hydrogen peroxide in0.1 M sodium acetate buffer. The sections were fixedin 4% formalin, counterstained with Gill's #3 hema-toxylin, rinsed, and cover slipped with Vinol 205 (AirProducts and Chemicals, Allentown, PA). Experimen-tal controls included tissue sections without the addi-tion of the primary and/or secondary antibody; posi-tive controls included murine spleen sections.

Experimental Design

Three representative BALB/cByJ and C.B-17 micewere killed by anesthesia overdose on days 2, 4, 6, 8,and 10 postinoculation. Two animals from eachstrain receiving an injection without virus served ascontrol animals. Inoculated (ipsilateral) and uninocu-lated (contralateral) eyes from a total of 34 animalswere removed and processed as described.

Using a Zeiss (Oberkochen, Germany) photomi-croscope III, positively staining cells were counted inthe uveal tract, vitreous, and retina. Three high-powerfields (HPF, with 100 mm2 = 1 HPF) from two repre-sentative stained sections were examined for each ofthe three animals for a given day postinjection, creat-ing the potential for 18 data points for each tissue permurine strain and time. The results were tabulated foreach day and each mouse strain. Group means andstandard errors of the means were calculated. Datafrom the two congenic strains were compared usingStudent's t-test to assess significant differences be-tween means. In the eyes stained for IgG, individualcell counts were not possible. The eyes were scored as+ if there was retinal staining and — if no retinal stain-ing was present. All cell counts and evaluations weredone in a masked fashion.


70 INVESTIGATIVE OPHTHALMOLOGY G VISUAL SCIENCE / January 1992 Vol. 33

Results

Ipsilateral (Inoculated) Eyes

Ciliary body: In BALB/c mice, injected eyes re-vealed progressive recruitment of each cell type in theciliary body (Fig. 1). Cellular infiltration began on day4 and peaked on day 10 postinjection. Thy 1.2-posi-tive cells were prominent with CD4 (Lyt 1) cells beingslightly more numerous than CD8 (Lyt 2) cells(CD4:CD8 = 1.5:1). The most frequent cell typesidentified were Mac and la cells with numbers in theciliary body approaching 200 ± 19 cells/HPF forMac+ cells by day 10 (Figs. 2A-B).

The C.B-17 mice showed trends similar to thoseseen in the BALB/c mice with all cells seen in theciliary body by day 4. Unlike BALB/c mice, however,by day 10, there was a significantly abrogated Macresponse in the ciliary body of C.B-17 mice (80 ± 16cells/HPF) compared with the ciliary body of BALB/cmice (200 ± cells/HPF, P < 0.005). This contrastedwith early observations in C.B-17 mice where theretended to be larger numbers of Mac mononuclearcells and minimal staining for la markers comparedwith BALB/c mice (Figs. 2C-D).

Vitreous: The vitreous of inoculated BALB/c eyesshowed progressive infiltration of all cell types. In gen-eral, cell numbers increased until day 8 and dimin-ished thereafter. T-cells first appeared on day 5; the

CD4:CD8 (Lyt l:Lyt 2) ratio on day 8 was 2:1. Maccells appeared in parallel with an la cell population.

The C.B-17 mice had a less prominent cellular reac-tion in the ipsilateral vitreous. On day 8, fewer Maccells were seen in the C.B-17 mice (7 ± cells/HPF)compared with the BALB/c mice (21 ± 3 cells/HPF,P < 0.005).

Inner and outer retina: In the retina of ipsilateraleyes, significant numbers of inflammatory cells infil-trated the intact retinal architecture (Fig. 3). Cell pop-ulations paralleled those found in the vitreous, andinflammation appeared to be greater in the inner ret-ina compared with the outer retina. Although cells ofall phenotypes were seen, Thy 1.2 staining was notinterpretable in the inner retina because ganglion cellsand inner nuclear layers normally stain for Thy 1.2.The IgG staining was not seen in control eyes but waspresent in both BALB/c and C.B-17 ipsilateral retinason days 2-10.

The inner retina of BALB/c mice showed a peak inCD4 and CD8 cells on day 10 and a CD4:CD8 ratio of1:1 (Fig. 3). Mac cells were the most frequent cellsdetected at each time with 61 ± 13 cells/HPF seen byday 8. la cells also were found on serial sections.

By contrast, C.B-17 mice tended to have fewer CD8cells in the ipsilateral retina, causing the CD4:CD8ratio to be greater in C.B-17 mice (2:1) than that in theBALB/c mice. The C.B-17 mice also showed an earlypeak of Mac cells without la staining on day 4 whereas

Lyt 2 Thy 1.2

Fig. 1. Graph of inflam-matory cell types found inthe ipsilateral (inoculated)ciliary body of BALB/c andC.B-17 mice after intraca-meral HSV-1 inoculation.


Fig. 2. Photomicrographs of the ipsilateral ciliary body (X160). (a) and (b) show a BALB/c ciliary body stained for la and Mac, respectively{day 10 p.i.). (c) and (d) show a C.B-17 ciliary body stained for la and Mac, respectively (day 4 p.i.j.

Fig. 3. Graph of cell types found in the ipsi-lateral inner retina.

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72 INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE / January 1992 Vol. 33

Fig. 4. Photomicrographs of a C.B-17 ipsilateral retina, day 4 p.i.(a) and (b) show la and Mac staining, respectively (X100).

both populations were detected in BALB/c mice(Figs. 4A-B). By day 8, C.B-17 mice had significantlyfewer Mac cells in the inner retina than did BALB/cmice (P < 0.005).

There were few inflammatory cells in the outer ret-ina of either BALB/c or C.B-17 animals. The generalpatterns of these cell types, however, followed thosefound in the inner retina (Fig. 4).

Choroid: In the BALB/c choroid, Thy 1.2, CD4,and CD8 cells appeared on day 6 and decreased afterday 8; the CD4:CD8 ratio (day 8) was 1:1 (Fig. 5). Thela and Mac cells were the most numerous cell type inthis tissue with the greatest numbers seen on day 9.

C.B-17 mice contrasted with the BALB/c micetrend to an earlier infiltration with Thy 1.2 and Maccells, but not la staining cells in the choroid on day 4.On day 8, there were significantly fewer Mac+ cells inC.B-17 mice (12 ± 3 cells/HPF) compared withBALB/c mice (77 ± 16 cells/HPF, P < 0.005).

Contralateral (Uninoculated) Eyes

Ciliary body: T-cells appeared in the contralateralciliary body of BALB/c mice between days 8 and 10,with a CD4:CD8 ratio of 3:1 by day 10. The Mac andla cells appeared simultaneously and in similar num-bers to those of T-cells (45 ± 13 cells/HPF). The cili-ary body of C.B-17 mice was devoid of all inflamma-tory cells.

Vitreous: In the contralateral BALB/c vitreous,CD4, Thy 1.2, and Mac cells appeared on day 10.

Thy 1.2

Fig. 5. Graph of cell typesfound in the ipsilateral cho-roid.


No. 1 MURINE H5V-1 CHORIORETINITIS / Zolros er ol 73

There were no la staining cells, and the Mac popula-tion was negative for this activation marker. The mostnumerous cells were Mac staining with 15 ± 3 cell/HPF. The C.B-17 mice had no vitreal cells.

Inner and outer retina: The cellular infiltration inthe contralateral retina of BALB/c mice was similar tothe phenotypic pattern in the vitreous (Fig. 6). Likethe ipsilateral eye, the retinitis was more severe in theinner retinal layers. On day 10, BALB/c mice showedfew CD4 (2 ± 0.6 cells/HPF and CD8 (1 ±0.2 cells/HPF) cells and a large infiltration of Mac cells (125± 19 cells/HPF) without the la cells or la activationmarker on the macrophages (Fig. 7). There was noIgG staining in the contralateral retina on days 2-8,but it appeared on day 10 (Fig. 8) in BALB/c mice.The C.B-17 mice had no inflammatory cells or IgG intheir contralateral retinas.

Choroid: The choroid of BALB/c mice showed adistinct cell profile different from that of the vitreousand retina (Fig. 9). T-cells were more numerous in thechoroid, with a CD4:CD8 ratio of 3:1 on day 10.Large numbers of Mac and la cells were seen, in con-trast to the absence of la cells in the contralateral vitre-ous and retina (Figs. 7B-C). All cell populations ap-peared on day 10. The C.B-17 mice did not have cho-roiditis, and inflammatory cells were not seen.

Discussion

We previously reported that, after intracameral in-oculation of HSV-1, Igh-1 congenic animals have dif-ferent rates of contralateral chorioretinitis; 75% inBALB/c, 30% in C.AL-20, and 5% in C.B-17 micehave contralateral disease.910 These disease patternsdo not correlate with systemic DTH response or hostpermissivity to HSV-1,12>13-17 suggesting that local ocu-lar immune phenomena may play a role in the devel-opment of the characteristic pathologic findings.Others described the general histopathologic featuresof this model, namely ipsilateral iridocyclitis and reti-nal sparing with contralateral chorioretinitis.519 Inthis study, we describe both the inflammatory cellsubpopulations involved in the von Szily model usingimmunohistochemistry and distinct cellular recruit-ment kinetics in inoculated and uninoculated eyes ofBALB/c and C.B-17 mice.

A vigorous T-cell response was seen in the anteriorstructures of the ipsilateral eye early after inoculationwith HSV. Further analysis found that both suscepti-ble BALB/c and resistant C.B-17 mice had TH/I(CD4) responses greater than TC/S (CD8) responsesin the ipsilateral ciliary body. This T-cell responsepreceded the later peak in Mac and la cell recruit-

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74 INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE / January 1992 Vol. 33

* >*--

Fig. 7. Photomicrographs of a BALB/c contralateral retina, day10 p.i. (a), (b), and (c) show Lyt I, la, and Mac staining, respectively(XI60).

ment. These kinetics suggest a helper T-cell-mediatedrecruitment of activated macrophages or antigen-pre-senting cells in response to viral challenge but do notaccount for differences in congenic disease patterns.

Although the architecture of the ipsilateral retina ispreserved, the posterior structures of the ipsilateraleye also appear to participate in the inflammatory pro-cess. It was noted that ipsilateral "retinal sparing" is arelative term, with the presence of mononuclear cells

and retinal folds differentiating inoculated eyes fromnormal ones.19 Our findings support this observation.A large number of T-cells and macrophages werefound in the ipsilateral retina and choroid, eventhough retinal architecture and cell layers were pre-served. The pattern of inflammatory cells found in theretina paralleled those found in the vitreous and cili-ary body. It would appear that the inflammatory cellsinvolved in the ipsilateral retinitis come from eitherretinal blood vessels or the ciliary body and not fromthe underlying choroid because most of the cells werefound in the inner retina with few in the outer retinallayers. The IgG staining also was detected in the ipsi-lateral retina beginning on day 2 postinjection, indi-cating an early breakdown in the blood-retina barrierand/or a rapid antibody response in the ipsilateraleye. These observations document the involvementof the ipsilateral retina in the inflammatory processand highlight the possibility of local antigen process-ing in these tissues.

Coinciding with the development of contralateralchorioretinitis, there is a significant immunohisto-

BFig. 8. Photomicrographs of BALB/c contralateral retinas

stained for IgG (X100). (a) shows the retina on day 8 p.i. Arrowindicates IgG staining seen in the choriocapillaris; the retina showsno staining. (8b) shows diffuse retinal staining on day 10 p.i.


No. 1 MURINE H5V-1 CHORIORETINITI5 / Zolras er ol 75

Lyt 1 Lyt 2 Thy 1.2

Fig. 9. Graph of cell typesfound in the contralateral cho-roid.

Day pi.

chemical difference in ipsilateral eyes of the congenicmouse strains. BALB/c mice recruit large numbers ofMac and la cells in the vitreous, retina, and choroidthrough day 10 versus the abrogated cellular infiltra-tion in C.B-17 mice. This may represent downregula-tion of the local ocular immune response or moreefficient control of the replicating pathogen by HSV-resistant C.B-17 mice.

There was a trend in resistant animals toward anearlier peak of inflammatory cells, specifically, Maccells without la staining cells on day 4 in the ipsilateralciliary body, inner retina, and choroid of the C.B-17mice compared with BALB/c mice. Cell numbers atthis early time were too small for statistical signifi-cance. Preliminary attempts to characterize this cellpopulation further suggest that these cells stain posi-tively with Asialo GM1 (Wako, Dallas, TX), a markerfor natural-killer cells, certain T-cells, and macro-phages (unpublished results). Because the T-cell popu-lation found in the C.B-17 mice at this time did notaccount for all of these Mac+ la - cells, they may bemacrophages that lack la activation markers or natu-ral-killer cells. Two other early trends were observedin the ipsilateral eye. The retina of C.B-17 mice had agreater CD4:CD8 ratio than BALB/c mice (2:1 versus1:1), and the choroid of C.B-17 mice showed an ear-lier T-cell response than BALB/c mice. These trendssuggest that C.B-17 mice may have an earlier helperT-cell-mediated recruitment of other inflammatorycell populations (Mac cells). This more efficient re-

sponse may assist in modulating the development ofcontralateral disease.

As previously reported, a striking feature of themodel is the lack of clinical and histologic evidencefor inflammation in the contralateral eye of C.B-17mice. Immunohistochemical data in this report con-firm these observations. The contralateral retina, vitre-ous, and choroid were normal in C.B-17 mice despitethe presence of HSV-1 at day 10 in these structures.Other investigators showed that virus was present inthe contralateral eye of BALB/c mice after infectionwith HSV-2, even though the contralateral eye wasmicroscopically normal.14 The absence of immunecells in the contralateral eye despite the presence oflive HSV suggests that immunologic events in the ipsi-lateral eye, regional lymph node, or spleen are criticalto prevent contralateral chorioretinitis throughunique cellular or humoral mechanisms.

By contrast, the contralateral retina and choroid ofBALB/c mice characteristically were destroyed. Inour study, there was an absence of inflammatory cellsuntil day 8. All cell populations were detected in thechoroid by day 8 and intensify by day 10. Mac cellsparalleled la cells as the most frequent cell type. In theT-cell population, CD4 cells were more commonthan CD8 cells. This cellular infiltration coincidedwith the second wave of virus described in the contra-lateral eye on days 7-10 in another study.20 By con-trast to the choroid, where all cell types were identi-fied, only Mac cells without markers for la antigens


76 INVESTIGATIVE OPHTHALMOLOGY 6 VISUAL SCIENCE / January 1992 Vol. 33

were found in the contralateral retina of BALB/cmice, supporting the observation that the inflamma-tory cells in the retina appear to originate from theretinal vasculature or the ciliary body and vitreouscavity and not from the choroid. With contiguous in-filtration from the underlying choroid, a similar dis-tribution of inflammatory cell subpopulations wouldbe expected; this was not found.

The significance of this distinct mononuclear cellpattern is not understood. Although lymphocyte-de-pletion studies, nude mouse experiments, and im-munohistopathologic findings establish a critical rolefor T-cells in the generation of HSV-mediated disease,our study supports a role for Mac cells and/or natural-killer cells as the effector cells mediating the retinaldestruction.2122 We did not find CD4 and CD8 cellsin the contralateral retina. The marker Thy 1.2 couldnot be assayed in the retina, and it is possible thatT-cells without markers for helper or suppressor sub-populations were present but undetected. Neverthe-less, most of the mononuclear cells stained for Macantigens. It is possible that the Mac mononuclear cellswithout la markers found in the retina represent ei-ther inactivated macrophages or natural-killer cells.Both cells stain positively for Mac-1. Retinal sectionsstained with Asialo GM1 antibody were positive forthis natural-killer cell marker and support their possi-ble role. The appearance of Mac+, Asialo GM-1+,and la- cells in the retina on day 10 postinjectionfollows closely the second wave of virus in the contra-lateral eye and represents an appropriate time se-quence for activated natural-killer cells.23'24 Other in-vestigators reported that these cells are effective in kill-ing virus-infected target cells in both in vitro and invivo studies and found similar murine strain-specificdifferences in natural-killer cell activity.25'26

Although we cannot define exact pathophysiologicmechanisms on the basis of histopathologic findingsalone, our study suggests some interesting hypothesesin the generation of herpetic ocular disease after ACinoculation. First, the marked cellularity of the uvealtract and the ipsilateral retina early after virus inocula-tion compared with the paucity of immune cells in thecontralateral eye supports a role for ipsilateral localocular antigen processing and subsequent immuno-regulatory events that modulate the generation of con-tralateral disease. Second, the predominance of Maccells without la markers in the contralateral vitreousand retina of susceptible BALB/c mice on day 10 im-plicates this mononuclear cell subpopulation as animportant mediator of the necrotizing contralateralretinitis. Third, gene products linked to the Igh-1locus appear to regulate the development of contralat-eral disease in part through disparate mononuclearcell subpopulations (most significantly by late recruit-ment of Mac and la cells in the ipsilateral and contra-

lateral choroid and ipsilateral retina of susceptibleBALB/c mice). It is expected that further refinementof this model will emerge from studies that examineother local sites of immune function (regional lymphnodes), noncellular (humoral) immunity, and macro-phage and natural-killer cell populations.

Key words: chorioretinitis, herpes simplex virus (HSV-1),Igh-1 locus, murine

Acknowledgments

The authors gratefully acknowledge the expert technicalassistance provided by Ms. Beverly A. Rice, BA, and Ms.Amy Kupferman, BA.

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immunohistopathologic findings in herpes simplex virus ... virus chorioretinitis in the von szily...

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