Adaptive Immune System Flashcards
Response time of the adaptive immune system
Days to weeks
Adaptive Immunity
Memory, specificity and tolerance
Maturation of lymphocytes
B cells: BM then lymph nodes
T cells: BM then thymus
Spleen
Lymphoid follicles- B cells, follicular dendritic cells
Macrophages and plasma cells
Filters blood traps microbes and immune complexes
Mucosa-associated lymphoid tissue (GALT)
Waldeyer’s ring
Peyers patches in small intestine
Appendix
Lymphoid follicles in large intestine and rectum
B-cell maturation and differentiation
Intentional gene recombination produces variety in individual BCR’s
B-cell to mature B-cell which expresses receptors with specific variable portion on surface of Ig specific to particular antigen.
Can become a plasma cell
Can be influenced by Th Cell
B cell receptor
which detects antigen is antibody (immunoglobulin, Ig). Antibodies are
also secreted. A cell secretes antibody specific to only one antigen
Subclasses of antibody
IgG, IgA, IgM, IgD, IgE
Structure of antibodies
heavy and 2 light chains
both with variable & constant regions
Functions of antibodies
Antigen presentation
Activation of complement
Opsonisation for phagocytosis
Free antigen neutralisation
Major Histocompatibility Complex 1
Occurs on all nucleated cells
Binds to CD8+ T cells
MHC II
Occurs on antigen presenting cells
Dendritic cells, macrophages, B cells
Binds to CD4+ T cells
Antibody Mediated Immunity
Initial exposure
Primary immune response (IgM)
Secondary exposure
IgA and IgG release
T cell Maturation
T cell to CD8+/CD4+ T cell, if it strongly binds to MHC there is apoptosis to avoid developing autoreactivity.
If weak goes on to develop T cells with T Cell receptor for specific antigens
Th1 (CD4+)
Activates macrophages, NK, CTL
Secrete: IL-2, IFN-gamma, TNF - alpha
Th2
Activate B cells to produce antibodies
Secrete: IL-4, IL-5, IL-6, IL-10, IL-13
Th17
Protect mucosal surfaces from microbes
Secrete: IL-17
Activates PMNs and monocytes
T regulatory cells
exert a controlling and regulatory influence on immune responses
cytotoxic T cells (CD8+)
secrete IFN and can kill cells infected by intracellular microbes eg viruses and some bacteria, and tumour cells.
CD4+ T cells
Th0 (naive T helper cell) binds to MHCII and can become memory T helper cell (Specific T cell receptor) or effector T helper cell (release cytokines which activate Eosinophils, macrophages, NK cells, CD8+, B cells)
CD8+ T cells (perforin and granzyme mediated apoptosis)
Cell expresses MHCI which activates CD8+ T cells resulting in the release of perforin and granzyme. Perforin creates a pore in the cell membrane and the granzyme enteres the cell which triggers apoptosis.
CD8+ T cells (fas-mediated apoptosis)
Nucleated cells infected with some viruses upregulate fas expression (CD95)
When fas antigens present with MHC I molecules to CD8+, this causes the CD8+ cell to express a fasL receptor on their cell membrane
Binding of fas with fasL causes target cell apoptosis
Lymphoid Tissues Primary
(thymus, bone marrow) where T and B respectively mature
Lymphoid Tissue Secondary
(lymph nodes, spleen, tonsils, adenoids, intestine/Peyer’s patches) where
lymphocyte responses to foreign antigen are initiated
