Cell Types and their Functions divided into B T and NK cells lymphoblasts lymphocytes that have interacted with antigens and proliferated eventually differentiate into effector or memory cells 5 10 of cells in blood large granular lymphocytes found in tissues of body but mostly in circulation contain cytotoxic substances important for protection against viruses tumors basically do same job as cytotoxic T cell but in innate response provide innate immunity against intracellular infections viral two effector functions cell killing and secretion of cytokines well developed cytoplasm with cytotoxic granules circulate in blood no rearrangement of B or T cell receptor genes secrete cytokines that prevent viral replication and help activate T cell mediated immunity Two major classes of NK cell receptors Ig like domain for ligand binding and lectin like domain lectin like receptors for ligand binding Some receptors are on all NKG2D but individual NK cells can express different receptor combinations NKG2D is lectin like and binds to MIC A and B MIC A and B are similar to MHC I heavy chains produced by infected gut epithelial cells Other NK cell receptors can recognize MHC I molecules and provide inhibitory signal healthy cell high levels of MHC I inhibitory and low numbers of stress induced activating Innate immunity involved in the capture engulfment and killing of microbes phagocytic cells short lived die at site of infection pyogenic pus former Lymphoid Cells Natural Killer Cells Neutrophils Mononuclear Phagocytes monocyte progenitors bone marrow pro monocytes blood monocytes monocytes circulate for 8 hours in blood migrate to tissues now they are macrophages monocytes are in peripheral blood and macrophages are in tissues differentiation from monocyte to macrophage monocytes enlarge 5 10 times increased organelles increased phagocytic ability production of hydrolytic enzymes Dendritic Cells Mast Cells Eosinophils Basophils Megakaryocyte Erythrocytes M cells secretion of soluble factors possess high levels of MHC class II also class I process and present peptide antigens to T cells follicular dendritic cells hold intact antigens in areas of lymphoid tissue not related to dendritic cells found in germinal centers In the gut take up and process antigens and either present them to T cells in Peyer s patches or migrate to mesenteric LN don t need M cells when outside Peyer s send dendrites out between cells to capture antigen found in skin connective tissues and mucosal epithelium of respiratory and digestive tracts unknown origin differentiate in bone marrow mature in tissues when activated they degranulate releasing mediators that cause vasodilation increased vascular permeability and attract leukocytes 1 6 of cells in blood granular leukocytes some phagocytic activities mainly for extracellular killing of large parasites usually bind to antibody coated parasite and release granule contents 2 of cells in blood very similar to mast cells in morphology release electron dense granules in cytoplasm during allergic reactions produced in bone marrow 1 of cells in blood but larger than red blood cells responsible for production of blood platelets large lobulated nucleus function determined by cytokines including thrombopoeitin red blood cells carry immune complexes to liver cleared by Kupffer cells specialized epithelial cells in Peyer s patches don t secrete digestive enzymes or mucus and lack glycocalyx allows M cells to take up intact organisms take in pathogens and transport them across epithelium transcytosis into Peyer s patches