Immunology 2 Flashcards

Question

B cell expansion

Answer 1

takes 4 - 5 days to complete naive to activated to effector effector cannot be maintained so eliminated eventually activated to memory B cells

Answer 2

commonest primary defect of specific immunity IgA is associated with mucous membrane so recurrent infections IgG can compensate but over reactive so linked to autoimmune disorders as produces autoantibodies also linked with allergies

Answer 3

deficiencies born with and normally X linked or autosomal recessive

Answer 4

is a region of DNA that encodes a group of molecules known as MHC proteins it is the most gene dense region of the mammalian genome proteins encoded by MHC are expressed on cell surface in humans MHC genes = HLA human leukocyte antigen letters following HLA isotypes are termed based on different DNA sequences that encode the particular isotype

Answer 5

present both self antigens and nonself antigens MHC class I and class II only have one peptide binding grove and each MHC molecule can only present one peptide at a time broad specificity

Answer 6

alpha chain complexed to beta 2 microglobulin isotypes: HLA - A/B/C/D/E/F/G etc present endogenous antigens (self antigens) + viral proteins presents to CD8 + cytotoxic T cells widely expressed on all nucleated cells and normally the MHC class I is complexed with self peptides

Answer 7

both alpha and beta chain isotypes: HLA - DM/DO/DP/DQ/DR present exogenous antigens (bacterial proteins) presents to CD4+ T helper cells expressed only by certain cells of the immune response e.g. dendritic cells, macrophages, B cells.

Answer 8

the cell samples its own intracellular proteins and presents them on MHC I cytosolic proteosome which degrades proteins into peptide fragments the peptide fragments (5 - 15 aa in length) are transported to ER via protein TAP antigen (peptide fragment) + MHC are complexed physically in the endoplasmic reticulum

Answer 9

exogenous peptide is phagocytosed in the cell and held in the phagosome phagosome fuses with lysosome and exogenous peptide is broken down into fragments endosomes containing MHC class II fuse with peptide fragments

Answer 10

not all individuals with at risk allele will develop the disease but most cases associated with obvious immune pathology: chronic inflammation arthritis autoimmune diseases are associated with specific HLA

Answer 11

90% of affected have HLA - B27 10% of normal population has HLA - B27

Answer 12

T cell = cellular arm of adaptive immunity B cell = humoral arm of adaptive immunity BCR are specific for antigen TCR are specific for antigen/MHC combination TCR only exists as cell surface receptor TCR diversity is by gene rearrangement MCR diversity is by somatic hypermutation

Answer 13

fragmented LINEAR antigenic peptides

Answer 14

secreted short range effector cytokines to recruit B cells and macrophages

Answer 15

bind and directly kill

Answer 16

suppress response to self antigens and shut down T cells when infection cleared

Answer 17

each T cell is specific for one antigen/MHC combination variability is achieved at the antigen binding region antigen binding domain has 3 hypervariable regions diversity is achieved by gene rearrangement

Answer 18

for alpha chain: V + J | for beta chain: V + D + J

Answer 19

T cells are long lived thymocytes = immature, intrathymic T cell precursors thymocytes become educated and MHC restricted in the thymus to become = mature T cells mature T cells migrate to secondary lymphoid organs

Answer 20

large in children and shrinks with age subcapsular zone contains early progenitor cell cortex packed with developing T cells medulla contains fewer but more mature T cells thymus contains many epithelial cells, macrophages and dendrites for antigen presentation and T cell education all possible antigens in the body are produced by cortical epithelial cells and presented to developing T cells

Answer 21

MHC class I + II growth factors

Answer 22

step 1: naive thymocytes enter the thymus and undergo gene rearrangement to display different TCRs. They are double negative i.e. CD4 + CD8 step 2: positive selection double negative t cells undergo positive selection and co receptor engagement. only T cells that bind appropriately to MHC molecules on cortical epithelial cells survive. they are now double positive step 3: negative selection eliminates self reactive T cells when it encounters self peptides on dendritic cells in the medulla. results in single positive T cell step 4: maturation useful T cells that dont interact with host protein are single positive and are said to be mature, MHC restricted and antigen naive.

Answer 23

step 1: double negative in subcapsular region step 2: positive selection (removes useless) double negative --> double positive by cortical epithelial cells step 3: negative selection (removes self antigens) double positive --> single positive by dendritic cell + medullary macrophage step 4: maturation go to periphery

Answer 24

although mature they are said to be antigen naive as they have not encountered their antigen yet a positive interaction allows the activation of the T cell into an effector T cell

Answer 25

helper cells produce many cytokines TNF alpha and IL - 1 cytokines in turn activate other immune cells: B cells, phagocytes, eosinophils, CD8+, macrophages 2 types: Th1 = viruses and bacteria via IFN gamma Th2 = parasites + worms via IL-4 and IL-5

Answer 26

once activated --> effector CD8+ cytotoxic T cell lymphocytes within the cytoplasm there is a full range of cytotoxic protein e.g. perforin or granzyme B and other molecules pumped directly into infected or tumorigenic cells which will directly kill it

Answer 27

impairment in T cell function is associated with B cell dysfunction most defects are combined immunodeficiency

Answer 28

neonates born with defect in T cell population will result in infants with major failure in both T and B cells failure to thrive chronic diarrhoea respiratory infections die before 2 years old cause: deletion of portions chromosome 22 development defects of: heart parathyroid + thymus