434 Final exam Questions with Complete

434 Final exam Questions with Complete Solutions (Latest 2025)

isotype switching: Describe the general mechanism of each,

what they accomplish, and which cells they occur in. -

Correct Answers ✅General Mechanism:

somatic recombination process uses AID enzymes that attach a different heavy chain constant region gene to the existing variable region. T helper cell interaction with B cells trigger isotope switching --> T dependent

Accomplish:

change the class of antibody thus the function while preserving the antigenic specificity of the antibody antibody

• NO junctional diversity

Cells:

***just in B cells

somatic recombination: Describe the general mechanism of

each, what they accomplish, and which cells they occur in. -

Correct Answers ✅General mechanism:

occurs between gene segments in the immunoglobulin loci.

RAG enzymes: RAG1 and RAG2 cut DNA and initiate somatic

recombination in pro-B and pre-B cells

• daughter cells can skip somatic recombination

***both B and T cells 1 / 3

434 Final exam Questions with Complete Solutions (Latest 2025) the 12/23 rule (12 spacer can only join to a 23 to ensure gene segments arranged in correct order)

- Light chain: only VJ are rearranged C is constant = L-V-J-C

(V-J = variable region)

- Heavy chain: VJD are rearranged C is constant = L-V-D-J-C

Accomplishes:

• combination of randomly selected gene segments-->

creates combinational diversity and junctional diversity

Cell involved:

T and B cells

somatic hypermutation: Describe the general mechanism of

each, what they accomplish, and which cells they occur in. -

Correct Answers ✅General Mechanism:

• occurs in germinal center of secondary lymphoid tissue,

where there is an increase of point mutations initiated by AID enzyme throughout variable regions DNA segments of immunoglobulin genes in activated Bcells

• T helper cell CD40L with naive B cells trigger somatic

hypermutation--> T dependent

Accomplishes: 2 / 3

434 Final exam Questions with Complete Solutions (Latest 2025)

• the way the adaptive immune system evolves with the

pathogen in our bodies.

• controls immunoglobulin affinity maturation and increases

the affinity pool of the antibody against the antigen

Cells:

***occurs in only B cells (Ig affinity maturation = somatic hypermutation + clonal selection) Compare and contrast positive and negative selection.Identify the goal of each, how and where they occur, and what cells they occur in. - Correct Answers ✅Positive

selection:

goal: ensures that only useful T cells that are able to bind to

MHC are released to the periphery. --> if no affinity for MHC-- > apoptosis

• determines CD4 or CD8 expression on T cells by

where:

• cortex of the thymus
• cortical thymic epithelial cells

how: double positive T cells bind Cortical Epithelial Cells

express MHC Class II for the purpose of T cell positive

• / 3