3. Lymphoid II Flashcards
Humoral immunity
manifested by production of Ab by plasma cells
cell’s presence not required for Ab to react with the antigen
Cell mediated immunity
the cell’s presence is required as it performs a function such as killing a cell
2 major lymphocyte development site
Thymus, Bone marrow
secondary lymphoid organs
lymph nodes, spleen
Bursa of Fabricius
removal of Bursa of Fabricius -> absence of plasma cells, absence of germinal centers, failure to develop Ab,
(Bone marrow equivalent)
T lymphocyte vs B
80% of blood lymphocyte vs 15%
cannot be differentiated from each other in stained blood film.
Both proliferate in lymphoid organs
proliferation -> clone of identical activated cell + memory.
Both can circulate/recirculate/reenter blood.
T lymphocyte vs B: Origin
T: lymphoid stem cell originated in bone marrow -> enter blood -> thymus -> cortex -> proliferates -> mature T lymph -> enter blood
B: bone marrow -> matures in marrow -> enter blood
T lymphocyte vs B: recirculation
T: most are recirculating pool
B: more likely to be sedentary (lifespan 1 week)
T lymphocyte vs B: receptor
B lymphocyte have plasmalemma-bound immunoglobulin with which it binds its specific antigen. (B cell receptor)
T cell has T cell receptor for a specific antigen. The receptor is NOT immunoglobulin but does bind with the same antigen that a Bcell binds
T lymphocyte vs B: infection type
T: viral, fungal, tumor cell, intracellular bacterial infections, allografts.
B: extracellular bacterial infections
T lymphocyte vs B: marker
T helper, killer have plasmalemmal surface markers that allow their identification
B can be identified by Ab they produce which is attached to their cell surface (plasmalemma)
T lymphocyte vs B: factory
Helper T - cytokin factory
B cell - Ab factory
CD4+ CD8+
CD4+ T cells are T helper cells
CD8+ T cells are cytotoxic cells
Helper T bind to antigen upon meeting B cell which has bound to the same antigen it recognizes the cell and allows the B cell to differentiate into plasma cell and secrete Ab.
cannot differentiate into plasma cells without participation of T-helper cell
Cytotoxic (killer) T lymphocytes kill tumor foreign and virus infected cells
Killer T cells need to receive a signal from a T helper cell before killer cell is capable of killing a cell. The T helper cell releases a cytokin
cytotoxic T lymphocytes kill cells by binding to target cells -> releasing perforins, glycoproteins which make a hole in the cell wall.
The target -> leaving it incapable of maintaining its cytoplasmic integrity -> death
Killer cell then goes to another target
killer T lymphocytes also release granzymes which enter the target cell disrupt its metabolism casing it to undergo apoptosis.
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