Antigen presenting cell قسم تقنيات التحليلات المرضية Lec3 Antigen presenting cell قسم تقنيات التحليلات المرضية مادة المناعة النظري- المرحلة الثالثة م.م. رشد اياد عبد الحميد 2018-2019

B lymphocyte B lymphocyte 15-35% of total lymphocytes Plasma cells (effecter B-cells): have lower levels or no membrane-bound antibody, synthesize and secrete a hundred to thousands of antibodies. Many of plasma cells die within a few days. Memory B cell have longer life span than naïve cells and express the same membrane bound Ab as their parent B-cell B cell markers ( Receptors & Molecules) Receptor: Fc – receptor (FCR) for IgG & IgM. IgM and IgD (Ag receptor). Complement component receptor (C3b receptor). Insulin receptor Molecules: Class I and Class II MHC Specific CD marker: CD 19, CD 20, CD 21

Natural Killer cell -Non T non B large granular lymphocyte -Not present at early & old ages so increase risk of cancer at those ages -Kills in a non specific (innate immunity) - non MHC restriction - not needs sensitization - not needs APC - no memory - so belong to non specific immunity. - Specific Marker CD 56+ve

Another cell type has been recognized which is NK1-T cell, this cell has some of the characteristics of both T cells and NK cells. Like T cells, NK1-T cells have T cell receptors (TCRs).Unlike most T cells, the TCRs of NK1-T cells interact with MHC-like molecules called CD1 rather than with class I or class II MHC molecules. Like NK cells, they have variable levels of CD16 and other receptors typical of NK cells, and they can kill cells. A population of triggered NK1-T cells can rapidly secrete large amounts of the cytokines needed to support antibody production by B cells as well as inflammation and the development and expansion of cytotoxic T cells.  

NK cells cytotoxic for tumor cells , viral infected cell. - It have receptor for FC region of Ab (CD16) and have receptor for TNF and IL2 NK cells cytotoxic for tumor cells , viral infected cell. CD16 bind with FC region of Ab on tumer cell then perforating cell membrane by inserting perforin into cell membrane and release: Protease =degrade protein in cell membrane. Nuclease=degrade nucleic acid. TNF=prevent protein synthesis ; result in cell lysis.

Antigen presenting cell (APC) Monocyte in the blood(1-6% of WBC) circulate for 3 days then migrate to tissue as a macrophage like alveolar cell in the lung,kupffer cell in the liver, osteoblast in the bone, histocytes in connective tissue and glail cell in the brain where they live for months and when activated they become APC where they have B7 molecule & Class II MHC; activation of macrophage by phagocytosis, Gamma-interferon & cytokines from T helper cells as IL2,IL12 while IL 8 is a chemotactic.

- Identifications of Microbes (Ag) by recognition Recptor as TL R Functions of APC: - Identifications of Microbes (Ag) by recognition Recptor as TL R -Engulfment (Phagocytosis) into phagosomes - Distraction of the Ag by Lysosomes in phagolysosome with preserving of the Epitope -Presents the epitope in the groove of MHC class I or class II on their surface for CD8 &CD4 respectively in association with B7 molecule.

T Cells Only Recognize Antigen Associated with MHC Molecules on Cell Surfaces

APC include (any cell have B7 molecule and class II MHC): Dendritic cells B lymphocytes Macrophages Langerhans cell They process the Ag & present it to T lymphocytes with class I for CD8+ cells or Class II for CD4+ cells also they deliver B7 Molecule to react with CD28 on T helper cells.