Inappropriate Immune Response Flashcards
what are the four types of hypersensitivity reaction
immediate hypersensitivity, autoantibodies, deposition of immune complexes, T-cell mediated tissue injury
what is immediate hypersensitivity
stimulation of mast cells by crosslinking of FcR bound IgE
vapid after exposure to antigen, called allergy or atopy and has strong genetic disposition
what do mast cell mediators cause
increased vascular permeability, vasodilation, bronchial and muscle contraction, local inflammation
what are allergens
require repeated exposure before substance triggers immune response, many allergens are small, glycosylated molecules with high solubility in bodily fluids
they no not trigger an innate response, hence no TH1 or macrophage activation
IL-4 promotes TH2 development and antibody class switching to IgE
what are autoantibodies
act by three mechanisms;
activate complement and stimulate phagocytosis (haemolytic anaemia)
can recruit neutrophils which cause tissue damage (glomerular nephritis)
can bind to receptor and stimulate or inhibit function
what are immune complexes
systemic diseases
can occur after multiple injections
usually occurs in small vascular beds like joints and renal glomeruli, leads to complement activation and FcR mediated response
what is cell mediated tissue injury
delayed type hypersensitivity and cytotoxiciy
mediated by TH1 and CD8 cells
release IFNgamma to activate macrophages and TNF to induce inflammation
tissue damage caused by hydrolytic enzymes, ROIs (reactive oxygen intermediate) and cytokines
what is autoimmunity
results from failure or breakdown in mechanisms normally responsible for maintaining self tolerance
can be systemic or organ specific
once initiated can result in epitope spreading resulting in chronic disease
what is genetic susceptability
inheritance of particular alleles increases risk
often associated with HLA
what immune considerations are made in transplantation
recognition of foreign MHCs (major histocompatibility complexes)
donor tissue killed by T cells, require blood and tissue typing
graft versus host disease
how is blood typing done
ABO system
antigens on surface of RBCs
everyone has basic glycolipid antigen (O), some people have attached carbohydrate groups (A or B)
we produce antibodies against antigens we dont have
the recepient must not have antibodies against donor antigen
what is congenital immunodeficiency
X-linked agammaglobulinemia
severe combined immunodeficiency
what is acquired immunodeficiency
as a result of infection, cancer or drug treatment
HIV/AIDS
what is HIV
human immunodeficiency virus
infects dendric cells and carried to lymph nodes, activation of CTLs and antibody production results in partial control of infection
infects T cells via CD4 and chemokine receptors
gradually causes lymphopenia
patient dies of opportunistic infections
