cell mediated immunity and lymph ontogeny

Question 1

CD8 T cell clonal activation

Answer 1

• peptide antigen presented on class 1 HLA

- downstream proliferation & differentiation to cytotoxic T and memory cells

Question 2

killing mechanism of cytotoxic T cells

Answer 2

1. release cytoplasmic granules when they bind, which punch holes in the membrane, called perforin
2. release enzymes which travel through the holes and get inside the cell
3. release cytokines (TNF) inducing apoptosis

antigen specific

Question 3

lymphocyte ontogeny

Answer 3

• T cell precursors from marrow and thymus

- after maturation in thymus, export T cells to secondary typhoid organs

Question 4

B cell lineage

Answer 4

• haematopoietic stem cells -> pre-B cell
• immature B cell (with surface IgM)
• mature B cell (with surface IgM and IgD)

Question 5

immunoglobulin genes

Answer 5

• heavy chains defined by constant regions
• multiple V, D, J axons recombine giving V- region variability
• recombination occurs independently of antigen
  exposure
• 1 gene set codes for heavy chain, 2x sets for light chains

Question 6

central tolerance

Answer 6

before leaving bone marrow, immature B cells are deleted if receptors have high affinity for self-antigens expressed in the marrow
(prevents self-reactivity)

Question 7

describe monoclonal

Answer 7

• Immortalised antibodies that can be engineered to be specific for particular target.
• Therapies used in chemotherapies
• Target specific cells not just everything dividing

Question 8

antibody class switching

Answer 8

• B cells able to switch antibody classes while maintain the same variable regions (antigen specificity)
• B cells can switch from one class to another by chopping out intervening sequences but still maintaining the same J, D or V meaning they retain the same antigen specificity (helper cells trigger deletion of genes)

initial make IgM –> IgG

Question 9

what gives the variable region its diversity

Answer 9

multiple V, D, and J axons that recombine

independent of antigen

Question 10

difference between B cell and T cell repertoire

Answer 10

B cell constantly being produced throughout life

Thymus shrinks with age and therefore fewer T cells later in life

Question 11

T cell ontogeny and T cell receptor genes

Answer 11

• development in the thymus
• multiple V, D and J axons recombine => V-region
• recombination independent of antigen
• T cells become committed to one Va and one Vb
• positive selection for HLA class 1 or 2 recognition (requires CD8 or CD4)
• negative selection process to rule out self-reactivity