Flashcards in Immunopathology II Deck (34)
what cell regulates both the humoral and cellular components of the immune system?
mature T4 cell
what is the cause of X linked agammaglobinemia?
mutation in tyrosine kinase gene responsible for pro/pre B cell signal transduction and continued B cell maturation
which antibody crosses the placenta?
patients with agammaglobinemia are susceptible to what types of infections?
enteric viruses and protozoa (no IgA)
what is the main feature of common variable immunodeficiency?
hypogammaglobinemia, usually all Ab classes but sometimes isolated to IgG
what is the mechanism of common variable immunodeficiency?
1. intrinsic B cell defect 2. abnormal T cell signaling to B cells (increased suppression or decreased helper activity) 3. inability of B cells to mature into plasma cells
what is the mechanism for selective IgA deficiency?
IgA and B cells fail to mature
what are the symptoms of selective IgA deficiency?
1. recurrent GI, respiratory, GU infections secondary to weakened mucosal defenses 2. increased risk for AI disorders (RA, SLE) 3. 40% have anti-IgA antibody
what is the cause of hyper IgM syndrome?
failure of T cells to: 1. induce B cell isotype switching from IgM to IgG/A/E, and 2. activate macrophages to remove intracelullar microbes
IgM producing B cells normally activate transcription genes that encode for other Ig isotypes via what signaling process?
signaling between CD40 on B cells and CD40L on Th cells
what are the levels of IgM in hyper IgM syndrome?
normal or elevated
hyper IgM syndrome has what type of inheritance?
1. X linked 70% 2. autosomal recessive for mutation of CD40 gene or activation induced deaminase enzyme required for switching
what are the clinical symptoms of hyper IgM syndrome?
1. recurrent pyogenic infections (no opsonizing IgG) 2. intracellular infections (P. jiroveci, no phagocytosis) 3. AI lysis (anti-RBC IgM reaction) 4. GIT lymphoid hyperplastic accumulations of IgM+ B cells
what are the features of DiGeorge syndrome?
T cell defect, hypocalcemia, cardiac abnormalities, cleft palate
what are the dysmorphologies of DiGeorge syndrome?
1. facial - low set ears, midline clefts, small mandible 2. cardiac - VSD, right subclavian artery derived from pulmonary artery
the x linked pattern of SCID involves what mutation? what is the result?
1. common gamma chain subunit of cytokine receptors 2. impaired lymphocyte development, proliferation, function
the autosomal recessive pattern of SCID involves what deficiencies? what are the effects?
1. adenosine deaminase deficiency - metabolites are toxic to lymphocytes 2. failure of MHC II expression - impaired T cell recognition of antigen
what are the clinical features of wiskott aldrich syndrome?
immunodeficiency, thrombocytopenia, eczema
what is the defect associated with WAS? what is the result?
WAS protein responsible for cytoskeletal maintenance and linkage of membrane receptors to cytoskeleton - progressive depletion of T and B cells
what are the clinical manifestations of WAS?
1. antibody levels normal (IgG) or elevated (IgA/E) with exception of IgM (low) 2. No antibody to polysaccharide antigen, poor antibody response to protein antigen 3. T cell deficit secondary to peripheral, progressive depletion in blood and nodal tissue
why is immunodeficiency linked to autoimmunity?
persistent infections leads to altered immune response and generation of auto reactive cells
what are the mechanisms of T cell loss in HIV infection?
1. viral replication in infected CD4 cells (cytopathic) 2. activation of uninfected CD4 T cells (apoptotic) 3. expression of HIV peptides on infected CD4 T cells (death by CTLs)
what are the effects of HIV infection?
1. selective lymphopenia of CD4 T cells with diminished T cell function 2. polyclonal B cell activation with hypergammaglobunemia yet impaired specific B cell response to new antigen 3. altered macrophage function with decreased MHC II expression and antigen presentation
what is the pathogenesis of B cell lymphomas following HIV infection?
increase in follicular T cells following HIV infection signals germinal centers to proliferate and become hyperplastic
what is the histologic appearance of P. jiroveci in the lungs?
alveoli filled with foamy exudate, thickened interstitium, coffee bean appearance with silver stain
what is the histologic appearance of candida?
pseudohyphae and blastoconidia (budding yeast)
what is the histologic appearance of pulmonary CMV?
enlarged, infected alveolar cells with a single basophilic nuclear inclusion, a perinuclear halo and multiple indistinct basophilic cytoplasmic inclusions
what is the main feature of progressive multifocal leukoencephalopathy?
reduced amount of myelin - loss of oligodendrocytes
what type of tumor is Kaposi's sarcoma?
endothelial type tumor, many RBCs, highly vascular