Interferons  Type I(,),  Autocrine and paracrine  Cause sequestration of lymphocytes  Promote diff. naïve T cells  Increase cytotoxicity of NK and CTLs  Upregulate expression MHC-I  Treatment of some tumors

Cells and Tissues of the immune system  The cells of the adaptive immune system are normally present: a)Circulating cells in the blood and lymph b)Anatomically defined collection in lymphoid organs c)Scattered cells in all tissues

 Lymphocytes  Antigen presenting cells(APC)  Effector cells

Cells of the immune system (lymphocytes)  Lymphocytes are the only specific cells and are responsible for specificity and memory  They are 3 subsets,different in functions and protein products but not in morphology 1-B cells 2- T cells(helper and cytotoxic) 3- Natural killer (NK) cells

B lymphocyte development  stem cell  Pro B cells CD19,CD10, µ heavy chain rearrangement  Pre B cells Pre antigen receptor expression  immature B cells IgM BCR expression,independent of antigen and their encounter with it,receptor editing,cell death,functional unresponsiveness  Mature B cells

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

T cell subpopulations T lymphocytes mature in the thymus *Mature T cells :Th and Tc,TR *T cells have CD4, CD8,TCR(αβ & ),CD28,CD40L,CD2,CTLA-4 (memory T cells have IL-7 R) *T helper cells have 2 subsets :Th1 and Th2 are differentiate by cytokine pattern that they produce. *Th1=IFN- *Th2 =IL-4, IL-5,IL-10, IL-13

Clonal selection

Effector cells  Activated Th cells  Cytolytic T cells  Plasma cells  Mononuclear phagocytes  Nk cells

Phagocytosis

NK cell activity

Dendritic cells  Coventional Dc  Plasmacytoid Dc