Immunology Today, vol. 7, Nos. 7 & 8, 1986

.letters- answer firmly 'Yes, probably'. Yet the demonstration of IL-2 receptors on B cells, allied with the data on function, make a persuasive picture. Nevertheless the growth of purified activated B cells in bulk cultures is transient and its level low in response to IL-2. Long-term B-cell lines remain an elusive goal. The best stimulator of B-cell growth continues to be a T cell. Perhaps crucially, when

cultured as single cells and activated, B cells do not become clonogenic in direct response to IL-2, according to Wetzel, but may respond to combin- ations of signals, perhaps as many as five.

The nature of B-cell growth was referred to during the meeting's opening session as a 'black box'. What followed in the subsequent two days did not lift the lid of that

box but, as these proceedings show, light was cast upon its walls.

The workshop was organized by Michael Julius, Tomas Leanderson, Fritz Melchers and Monte Wetzel. The Role of IL-2 in B-cell Physiology, published by Editiones Roche, is available free of charge on applica- tion to the Basel Institute for Im- munology, Grenzacherstrasse 487, CH-4005 Basel, Switzerland.

Anergy induced by cyclosporin and C. parvum

Sir, In their article on cyclosporin (CS) Klaus and Chisholm (Irnmunol. To- day, 1986, 7, 101-103) highlighted an apparent paradox. They pointed out that the evidence that CS inhibits IL-2 production in vitro seems incon- sistent with its action in vivo. They cited evidence to show that CS allows T cell priming in vivo, and presumably IL-2-dependent clonal expansion, to proceed while pre- venting effector T-cell development. At the risk of compounding their paradox, I would like to draw atten- tion to the striking similarities be- tween the anergic state the 'im- munosuppressive' agent CS induces and that found, ironically, following administration of the 'immuno- enhancing' agent C. parvum 1.

It is wise not to overgeneralize when attributing mechanisms to biological response modifiers be- cause the mechanism can depend upon variables such as dosage, route of injection, species and response under investigation. However, if two so disparate agents as CS and C. parvum are found to generate simi- lar states of anergy under particular treatment situations, it would sup- port the view of Klaus and Chisholm that CS operates in vivo by produc- ing subtle perturbations of the im- mune network. It also provides a framework within which to consider some of the immunoenhancing effects sometimes seen with CS 2-s, We have argued elsewhere 1 that the anergic state generated by C. par- vum can precede and may even be a prerequisite for immune enhance- ment; the same sequence of events may occur under certain circum- stances with CS.

The generalized anergic state that

develops following a single i.v. in- oculation of C. parvum ~ is transient, developing on day 6 and lasting 7- 10 days. Ongoing effector level T H cell responses but not type I T cell- independent responses, are depres- sed at this time. Primed cells are present throughout the anergic state. This was deduced from finding that 'unresponsive' T-cell popula- tions could transfer immunity adop ~ tively and that they would respond in vitro if lymphokine-containing Con A supernatants were added or if the cells were cultured in vitro for an extended period of time. We could find no evidence for the participation of suppressor cells in the generation or maintenance of the anergic state. We concluded that the state was due to lack of delivery of a differentiation/maturation signal to T H cells.

The state of continued priming under ~:over of immunosuppression that is induced by C. parvum seems therefore to be similar in most essen- tials to that induced by CS as des- cribed by Klaus and Chisholm. The consequences of removal of the im- munosuppressive block are therefore of some interest. In a murine sar- coma system we showed that recov- ery of TH-Cell responsiveness follow- ing the temporary anergy induced by systemic C. parvum, signalled com- mencement of T-cell-dependent tumor regression. We proposed that tumor regression was the result of a wave of differentiation in the accumulated population of primed T cells following removal of the block and therefore akin to the generation of a second set rejection mechanism. At the same time we noted that this response would be aided by a delay in the development of tumor-specific Ts cells which was also found in C. parvum-treated tumor-bearing mice. In fact the delay in Ts cell develop- ment may be consequent upon the

absence of effector T cells although direct evidence to support this view is lacking. As Klaus and Chisholm noted, under certain conditions CS has been shown to enhance immune responses 2-5. With CS, as with C parvum, the relative timing of the injections and dosage seem impor- tant but the fact that enhancement often follows termination of the un- responsive state seems at least con- sistent with the possibility that these agents may have similar modes of action under certain circumstances.

There are still questions as to how CS and C parvum cause T-cell an- ergy and if they share the same pathway. A unitary hypothesis would be that CS and C parvum both directly affect the production of a differentiation factor (and perhaps, in addition, IL-2). Even if IL-2 produc- tion is affected in vivo, minimal levels of IL-2 may be sufficient to maintain a primed state in cells responding to antigen while the lack of a dif- ferentiation factor may be more cri- tical. The possibility that high IL-2 levels aid differentiation also cannot be excluded. However, an alternative view, and one we prefer, is that correct T-cell trafficking and micro- environmental location are required for T-cell maturation. We have pre- sented evidence that C. parvum affects T-cell trafficking during aner- gy and Chisholm et al. 6 have shown that CS affects release of alloreactive blast ceils. Disturbances in trafficking could be a common mechanism but we would agree with Klaus and Chisholm that further studies in vivo are needed to define these anergic states and that "available tissue cul- ture systems cannot reproduce the microenvironments of lymphoid tis- sues."

Bill McBride Department of Radiation Oncology, UCLA

School of Medicine, Center for Health Sciences, Los Angeles, CA 90024, USA

189

r-letters Immunology Today, voL 7, Nos. 7 & 8, 1986

References

1 McBride, W.H. and Howie, S.E.M. (1984) Clin. Exp. ImmunoL 57, 139-148 2 Borel, J.F. (1981)in Transplantation

~ . and Clinical Immunology Vol. XlII

(Touraine, J.L., Traeger, J. and Betuel, H, eds) p.3, Excerpta Medica, Amsterdam. 3 Kunkl, A. and Klaus, G.G.B. (1980) J. Immunol. 125, 2526-2531 4 Klaus, G.G.B. and Kunkl, A. (1983)

Transplantation b6, 80-84 5 Thomson, A.W., Moon, D.K., Inoue, Y. et al. (1983) Immunology 48,301-308 6 Chisholm, P.M., Drayson, M.T., Cox, J.H. et aL (1985)Eur. J. Immunol. 15, 340-348

Immunosuppression mediated by seminal

plasma - fact or artefact?

Sir, Several studies have reported the immunosuppressive nature of com- ponents present in human seminal plasma (SP). Suppression of T- lymphocyte mitogenesis occurs as well as suppression of natural killer (NK) cell activity and their activation of lymphokines, inhibition of macro- phage function, and reduced ex- pression of complement and Fc re- ceptor expression on lymphoid cells I Io. Complete abrogation of lymphocyte function can be achiev- ed with low (less than 0.5% v/v) concentrations of SP, but the mole- cules responsible for immunosup- pression have not been identified.

We have evaluated the conditions necessary for SP to mediate suppres- sion of NK cytotoxicity and lympho- cyte mitogenesis, and our results suggest a possible mechanism whereby SP inhibits immune function. Previous studies showed that SP mediates the suppression of lympho- cyte responses in media sup- plemented with bovine serum. We have found that the presence of newborn calf serum (NBCS) or foetal calf serum (FCS) is essential to de- monstrate the inhibitory effects of SP on lymphocyte function and 11 response . We have shown that SP inhibits NK-mediated cytotoxicity when assays are performed in RPMl- 1640-medium containing 10% bovine serum, but not when assays are performed in either RPMl-1640- medium supplemented with 10% human plasma, or in HBI03 serum- free medium (New England Nuclear Research products). Addition of either NBCS or FCS to HBI03 medium allows SP to regain its sup- pressive activity, inferring that ex-

ogenous bovine serum components are essential for SP to mediate im- mune suppression. Similarly, we have found that SP suppression of lymphocyte activation by phyto- haemagglutinin is dependent on the presence of bovine sera; SP being unable to inhibit cell proliferation in the absence of exogenous bovine serum.

A possible mechanism whereby SP mediates inhibition of lymphocyte activity is suggested by previous work with polyamines such as sper- mine and spermidine. These are pre- sent in high concentration in SP, and have been shown to suppress lym- phocyte mitogenesis, but only in the presence of bovine or foetal bovine sera 12'13. This effect is due to the presence in bovine serum of an en- zyme, polyamine oxidase, which converts spermine to oxidized spermine14; the oxidized form hav- ing potent immunosuppressive effects 1 s. It remains to be confirmed that SP inhibition parallels these events, although studies in our laboratory have shown that the immunosuppressive factor in SP is of very low molecular weight, similar to that of polyamines, and that antag- onists of the enzyme polyamine ox- idase prevents bovine serum initiat- ing SP suppression.

It is therefore questionable whether results, generated in vitro in the presence of exogenous bovine serum components, directly relate to likely events in vivo, and it will be necessary to reaffirm the biological significance of SP in suppression of host defences. For example, one im- portant aspect to consider will be the interaction of SP with female genital secretions. Additionally, it will be essential to define the molecular species present in both SP and serum responsible for immunosuppression, and to confirm their mechanism of action. Whether bovine serum com-

ponents contribute to the biological effects of SP in other assays - for instance, suppression of macro- phage function has not yet been established. We would welcome in- formation and comments from other workers interested in this aspect of immunoregulation, who may have complementary evidence on the mechanism and relevance of SP-' mediated immunosuppression.

Robert C. Rees Pamela J. Vallely

Department of Virology, Unive~iO/ of Sheffield Medical School, Beech Hi//Road,

Sheffield SlO 2RX, UK

References 1 Sites, D.P. and Erickson, R.P. (1975)Nature (London), 253, 727-729 2 Lord, E.M., Sensabaugh, G.F. and Sites, D.P. (1977)J. Immunol. 118, 1704-1711 3 Marcus, Z.H., Freisheim, J.H., Houk, J.L. etal. (1978) C1in. ImmunoL ImmunopathoL 9, 318-326 4 Franken, D.R. and Slabber, C.F. (1981) Andrologia 13, 504-507 5 Majumbar, S., Bapna, B.C., Mapa, M.K. et al. (1982) Int. J. Fertil. 27, 224-228 6 Peterson, B.H., Lammel, C.J., Sites, D.P. etal. (1980) J. Lab. Clin, Med. 96, 582-591 7 Stankova, L., Drach, G.W., Hicks, T. et al. (1976)J. Lab. Clin. Med. 88, 640 8 James, K. and Szymaniec, S. (1985) J. Rep. Immunol. 8, 61-70 9 Rees, R.C., Vallely, P., Clegg, A. etaL (I 986)Clin. Exp. Immunol. 63, 687-695 10 James, K. and Hargreave, T.B. (1984) Immunol. Today 5, 357-363 11 Vallely, P. and Rees, R.C. C/in. Exp. ImmunoL (in press) 12 Williamson, J.D. (I 984) Nature (London) 310, 103 13 Byrd, W.J., Jacobs, D.M. and Amoss, M.S. (I 977) Nature (London) 267, 621-623 14 Labib, R.S. and Tomasi, T.B. (I 981) Eur. J. Immunol. 1 I, 266-269 15 Gaugas, J.M and Dewey, D.L. (1978) Br. J. Cancer39, 548

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