InterferonsInterferons Type I(Type I(,,),), Autocrine and paracrine Autocrine and paracrine Cause sequestration of lymphocytesCause sequestration of lymphocytes Promote diff. naïve T cellsPromote diff. naïve T cells Increase cytotoxicity of NK and CTLsIncrease cytotoxicity of NK and CTLs Upregulate expression MHC-IUpregulate expression MHC-I Treatment of some tumorsTreatment of some tumors

Cells and Tissues of the immune Cells and Tissues of the immune systemsystem

The cells of the adaptive immune The cells of the adaptive immune system are normally present:system are normally present:

a)Circulating cells in the blood and a)Circulating cells in the blood and lymphlymph

b)Anatomically defined collection in b)Anatomically defined collection in lymphoid organslymphoid organs

c)Scattered cells in all tissuesc)Scattered cells in all tissues

LymphocytesLymphocytes Antigen presenting cells(APC)Antigen presenting cells(APC) Effector cellsEffector cells

Cells of the immune systemCells of the immune system (lymphocytes) (lymphocytes)

Lymphocytes are the only specific Lymphocytes are the only specific cells and are responsible for cells and are responsible for specificity and memoryspecificity and memory

They are 3 subsets ,different in They are 3 subsets ,different in functions and protein products but functions and protein products but not in morphologynot in morphology

1-B cells1-B cells2- T cells(helper and cytotoxic)2- T cells(helper and cytotoxic)3- Natural killer (NK) cells3- Natural killer (NK) cells

B lymphocyte developmentB lymphocyte development stem cellstem cell Pro B cellsPro B cellsCD19,CD10, CD19,CD10, µµ heavy chain rearrangement heavy chain rearrangement Pre B cellsPre B cellsPre antigen receptor expressionPre antigen receptor expression immature B cellsimmature B cellsIgM BCR expression,independent of antigen IgM BCR expression,independent of antigen

and their encounter with it ,receptor and their encounter with it ,receptor editing,cell death,functional editing,cell death,functional unresponsivenessunresponsiveness

Mature B cellsMature B cells

B cell surface markersB cell surface markersB cell receptorB cell receptor(Ag recognition)(Ag recognition)CD19 CD19 (B cell activation)(B cell activation)CD21or CR2 CD21or CR2 (B cell activation and EBV receptor) (B cell activation and EBV receptor) CD25 CD25 (binds IL- 2)(binds IL- 2) CD27 (memory B cells )CD27 (memory B cells )CD40 CD40 (B cell activation)(B cell activation)CD80 or B7CD80 or B7(costimulator for T cell activation)(costimulator for T cell activation)CD81 CD81 (B cell activation)(B cell activation)

T cell subpopulationsT cell subpopulations

T lymphocytes mature in the thymusT lymphocytes mature in the thymus*Mature T cells :Th and Tc,TR *Mature T cells :Th and Tc,TR *T cells have CD4, CD8,TCR(*T cells have CD4, CD8,TCR(αβαβ & &

) ,CD28,CD40L,CD2,CTLA-4) ,CD28,CD40L,CD2,CTLA-4(memory T cells have IL-7 (memory T cells have IL-7 R)R)

*T helper cells have 2 subsets :Th1 and Th2 *T helper cells have 2 subsets :Th1 and Th2 are differentiate by cytokine pattern that are differentiate by cytokine pattern that they produce.they produce.

*Th1=IFN-*Th1=IFN-*Th2 =IL-4 , IL-5,IL-10, IL-13*Th2 =IL-4 , IL-5,IL-10, IL-13

Clonal selectionClonal selection

Effector cellsEffector cells Activated Th cellsActivated Th cells Cytolytic T cellsCytolytic T cells Plasma cellsPlasma cells Mononuclear phagocytesMononuclear phagocytes Nk cellsNk cells

PhagocytosisPhagocytosis

NK cell activityNK cell activity

Dendritic cellsDendritic cells Coventional DcCoventional Dc Plasmacytoid DcPlasmacytoid Dc