Lymphocytes Flashcards
Innate immune cells
neutrophils, monocytes, macrophages, dendritic cells, NK cells, complement
Innate immune characteristics
non-specific, rapid response; includes physical barriers like skins and mucus; has PRR to PAMPS and secrete lysozyme, complement, C-reactive protein, and defensins
Innate immune cells
lymphocytes
Adaptive immune characteristics
specific, slower but has memory; V(D)J recombination -> immunoglobulins
MHC I processing
Proteosome degrades endogenous peptide -> TAP allows peptide fragments into RER, loaded onto MHC I -> B2-microglobulin associates -> sent to cell surface
MHC I characteristics
HLA-A, B, C; expressed on all nucleated cells; present endogenous antigens to CD8+ CTL
MHC II processing
MHC loaded with invariant chain in the ER -> in endosome/lysosome the acidic pH cleaves the invariant chain leaving a CLIP peptide -> vesicle fuses with processed peptide and replaceds CLIP -> pMHC fuses with cell surface
MHC II characteristics
HLA-DP, DQ, DR; expressed on APCs; present exogenous antigens on CD4+ helper T cells
Natural killer cells (NK cells)
from lymphoid progenitor; recognizes by lack of class I MHC on target cells -> release perforin and granzyme to induce apoptosis; has Fc receptors for antibody-dependent cell-mediated cytotoxicity (ADCC)
B cell function
Recognize antigen (somatic hypermutation), produce antibodies (plasma cells), maintain immunological memory
T cell function
CD4+ T cells activate B cells, make cytokines to recruit phagocytes ; CD8+ T cells directly kill virus infected cells; type IV hypersensitivity
T cell maturation
Pre-T cells has V(D)J recombined B chain and pre-T alpha; becomes double positive (CD4+CD8+ and mature TCR) -> positive selection -> single positive -> negative selection -> naïve mature T cell
T cell differentiation cytokines
Th1 = IL-12; Th2 = IL-4; Th17 = TGF-B + IL-6
Positive selection
Thymic cortex; gets rid of T cells specific against self-MHC
Negative selection
Thymic medulla; gets rid of T cells with high affinity for self antigens
T cells activation with macrophages
Activated macrophages secrete IL-12 to differentiate into Th1 cells -> Th1 cells secrete INF-g to stimulate macrophages further
Th1 cell
differentiated by IL-12 and IFN-g; secretes IFN-g to activate macrophages and cytotoxic T cells; inhibited by IL-4 and IL-10
Th2 cell
differentiated by IL–4; secretes IL-4, IL-5, IL-10, IL-13 to recruit eosinophils and promote IgE; inhibited by IFN-g
Cytotoxic T cells
CD8+ binds to MHC I; kills virus-infected, neoplastic, and donor graft cells by releasing cytotoxic granules (perforin, granzyme)
Regulatory T cells
CD3+CD4+CD25+Foxp3+; maintain specific immune tolerance by suppressing CD4 and CD8 T cell effector function by direct contact or indirect (anti-inflammatory cytokines like IL-10, TGF-B)
Naive T cell activation
APC sample and process antigen on MHC; drain to lymph node and give signal 1 to TCR; signal 2 is CD28 on T cell to CD80/86 on APC; signal 3 is differentiation, APC secrete cytokines to do so
B cell activation and class switching
Th cell is activated -> BCR mediated endocytosis, presents on MHC II, and recognized by TCR on Th cell (signal 1) -> Th cell expresses CD40L which binds to CD40 on the B cell (signal 2) -> Th cell secretes cytokines that determine Ig class switching of B cell
Fab
fragment antigen binding, 1 antigenic specificity per B cells -> idiotype
Fc
fragment constant, carboxy terminal, complement binding, carbohydrate side chain
