front 1 What are the tenets of clonal selection theory? | back 1 Each lymphocyte has a unique receptor, receptors are made before infection, antigen selects the matching cell, the cell proliferates, clones become effector and memory cells, and self-reactive cells are eliminated |
front 2 Why is clonal selection theory relevant? | back 2 Explains specificity, immune memory, and how vaccines work |
front 3 What is the difference between stem cells and stromal cells? | back 3 Stem cells become immune cells, stromal cells support development |
front 4 How do stromal cells support development? | back 4 Through physical contact and soluble factors (cytokines) |
front 5 What are examples of stromal support? | back 5 SCF–Kit (contact) and IL-7 (cytokine) |
front 6 What happens in the Pro-B cell stage? | back 6 Heavy chain rearrangement |
front 7 What happens in the Pre-B cell stage? | back 7 Heavy chain made, pre-BCR forms, proliferation |
front 8 What happens in the immature B cell stage? | back 8 Light chain rearrangement and IgM expression |
front 9 What happens in the mature naïve B cell stage? | back 9 IgM and IgD expression, leaves bone marrow |
front 10 What is a pre-B cell receptor? | back 10 A test receptor for the heavy chain |
front 11 What is the purpose of the surrogate light chain? | back 11 Tests if the heavy chain works |
front 12 What are the surrogate light chains? | back 12 VpreB and λ5 |
front 13 How is the heavy chain tested? | back 13 Forms pre-BCR with surrogate light chain and must signal |
front 14 What is a productive rearrangement? | back 14 Functional receptor with correct reading frame and no stop codon |
front 15 What is a non-productive rearrangement? | back 15 Nonfunctional receptor due to frameshift or stop codon |
front 16 What determines if rearrangement is productive? | back 16 In-frame sequence, no stop codon, full protein |
front 17 What is the relationship between rearrangement and allelic exclusion? | back 17 Productive rearrangement stops the other allele; non-productive leads to trying the second allele |
front 18 What is the difference between heavy and light chain rearrangement? | back 18 Heavy chain has one chance; light chain can retry and edit |
front 19 What are the checkpoints of B cell development? | back 19 Heavy chain checkpoint, light chain checkpoint, self-tolerance checkpoint |
front 20 What proteins are expressed early in B cell development? | back 20 CD19 and IL-7 receptor |
front 21 What proteins are expressed mid-development? | back 21 Pre-BCR |
front 22 What proteins are expressed later? | back 22 IgM and IgD |
front 23 How does the heavy chain variable region attach to the constant region? | back 23 By RNA splicing |
front 24 What is recombination vs splicing? | back 24 Recombination is DNA-level VDJ joining; splicing is RNA-level joining to constant region |
front 25 Why is the order of constant regions important? | back 25 Determines antibody class |
front 26 What is the role of alternative splicing? | back 26 Allows IgM and IgD expression |
front 27 What happens during negative selection of B cells? | back 27 Self-reactive cells undergo apoptosis, anergy, or receptor editing |
front 28 What is apoptosis? | back 28 Programmed cell death |
front 29 What is anergy? | back 29 Cell becomes inactive |
front 30 What is receptor editing? | back 30 Light chain is changed to avoid self-reactivity |
front 31 Why can receptor editing only occur in light chains? | back 31 Heavy chain rearrangement is complete and cannot be redone |
front 32 What is central tolerance? | back 32 Removal of self-reactive cells in bone marrow |
front 33 What is peripheral tolerance? | back 33 Control of self-reactive cells outside bone marrow |
front 34 Why is peripheral tolerance needed? | back 34 Not all self-antigens are in bone marrow |
front 35 What are B1 and marginal zone B cells? | back 35 Innate-like, fast responders |
front 36 What are B2 cells? | back 36 Conventional adaptive B cells |
front 37 Where does T cell development begin and end? | back 37 Begins in bone marrow, ends in thymus |
front 38 What is a thymocyte? | back 38 Developing T cell |
front 39 What is the difference between cells entering and leaving thymus? | back 39 Entering are immature; leaving are CD4 or CD8 mature cells |
front 40 What is the role of the Notch receptor? | back 40 Drives T cell development |
front 41 What happens to the thymus over time? | back 41 Shrinks after puberty (involution) |
front 42 What are the regions of the thymus? | back 42 Cortex and medulla |
front 43 What happens in the cortex? | back 43 Positive selection |
front 44 What happens in the medulla? | back 44 Negative selection |
front 45 What are the stages of T cell development? | back 45 DN → DP → SP |
front 46 How long does T cell development take? | back 46 About 2–3 weeks |
front 47 What does the CD4 | back 47 CD8 flow plot show? / None → both → one |
front 48 What does the CD44 | back 48 CD25 flow plot show? / 44 → both → 25 → none |
front 49 What are double negative cells? | back 49 No CD4 or CD8 |
front 50 What are double positive cells? | back 50 Both CD4 and CD8 |
front 51 What are DN1 cells? | back 51 Earliest stage, entry into thymus |
front 52 What happens in DN2 cells? | back 52 TCR rearrangement begins |
front 53 What happens in DN3 cells? | back 53 β chain rearrangement and pre-TCR checkpoint |
front 54 What happens in DN4 cells? | back 54 Proliferation and CD4/CD8 expression |
front 55 What are αβ T cells? | back 55 Most common, adaptive |
front 56 What are γδ T cells? | back 56 Less common, innate-like |
front 57 What is the pre-TCR made of? | back 57 β chain + pTα + CD3 |
front 58 What is β-selection? | back 58 Checkpoint testing β chain function |
front 59 What is positive selection? | back 59 Keeps T cells that recognize self-MHC |
front 60 What is self-restriction? | back 60 T cells must recognize antigen with self-MHC |
front 61 What is the goldilocks model? | back 61 Binding must be just right |
front 62 What happens with weak binding? | back 62 Death by neglect |
front 63 What happens with strong binding? | back 63 Apoptosis |
front 64 What happens with intermediate binding? | back 64 Survival |
front 65 What happens with slightly high affinity? | back 65 Treg formation |
front 66 What is lineage commitment? | back 66 Becoming CD4 or CD8 T cell |
front 67 What determines CD4 vs CD8? | back 67 Type of MHC recognized |
front 68 What is negative selection? | back 68 Removal of self-reactive T cells |
front 69 What is self-tolerance? | back 69 Immune system ignores self |
front 70 What are mechanisms of negative selection? | back 70 Apoptosis, anergy, Treg formation |
front 71 What is AIRE? | back 71 Protein that presents self-antigens in thymus |
front 72 What is positive selection characterized by? | back 72 Cortex location, self-MHC recognition, ~5% survival |
front 73 What is negative selection characterized by? | back 73 Medulla location, removal of self-reactive cells |