immunity part 2 Flashcards
immune system dysfunctions:
1
2
3
hypersensitivity
autoimmune diseases
immune deficiency diseases
lack of response to antigens that is induced by exposure of lymphocytes to these antigens
immunologic tolerance
ability to discriminate between self and nonself antigens
immunologic tolerance
if immunologic tolerance fails->
autoimmunity
with immunologic tolerance:
normally, microbes are immunogenic[cause immune response], and self-antigens are
tolerogenic[do not cause immune response]
developing lymphocytes encounter self antigens in central lymphoid organs(bone marrow)
central tolerance
mature lymphocytes encounter self antigens in peripheral tissues (secondary lymphoid organs)
peripheral tolerance
central t cell tolerance normally deals with
cd4 t cells
central t cell tolerance->
self reactive tcells:
- negative selection or deletion
- development of regulatory t cells
peripheral t cell tolerance 3 ways
- regulatory t cells
- anergy
- deletion
blocks the activation of self-reactive lymphocytes
regulatory t cells
functional inactivation of t cells (lack of costimulation)
anergy
apoptosis of self-reactive lymphocytes
deletion
self polysaccharides, lipids, and nucleic acids: induce tolerance in
b cells
two types of cell tolerance in b cells
- central b cell tolerance
- peripheral b cell tolerance
-receptor editing
-negative selection (apoptosis)
what type of b cell tolerance is this
central b cell tolerance
-anergy
-excluded from lymphoid follicles
what type of b cell tolerance is this
peripheral b cell tolerance
immune response against self antigens
autoimmunity
the development of autoimmunity may be related to
- inheritance of susceptibility genes
- environmental triggers
must autoimmune diseases are
polygenic
autoimmune diseases often associate with particular HLA(MHC) genes that are inefficient at displaying self antigens:
- defective t cell negative selection
- may fail to stimulate regulatory t cells
infections may activate self-reactive lymphocytes in autoimmunity by:
- increased production of costimulatory molecules on APCs
- molecular mimicry
injurious or pathologic immune reactions
-immune response may be inadequately controlled
-directed against normal harmless antigens
hypersensitivity
what 3 things causes hypersensitivity
- autoimmunity :reactions against self antigens (failure of self-tolerance)
- reactions against microbes: excessive reactions or unusually persistent microbes
- reactions against environment: common allergens (pollen)
types of hypersensitivity
type I: immediate
type II: antibody-mediated
type III: immune complex-mediated
type IV: cell mediated (with t cells)
which types of hypersensitivity
-tissue reaction that occurs rapidly after interaction of antigen with IgE antibody bound to mast cell
-often developed in atopic individuals- sensitized to allergens
-environmental and food allergens
mild to severe reaction (asthma example)
type I
mediators that are released by mast cells after activation for type 1 immediate hypersensitivity:
1
2
3
- vasoactive amines
- lipid mediators
- cyotkines
causes vasodilation, increased vascular permeability, smooth muscle contraction, and increased secretion of mucus
histamine-> vasoactive amines
[mediator for type I]