Week 2 Flashcards
(32 cards)
Genes for immunoglobulins are unlike other human genes in that
somatic recombination occurs before mRNA is transcribed
and there is less Ig genetic material in mature B cells than in other somatic cell
The gene segments needed to encode the variable region of a k chain are
one Vk plus one Jk.
Combinatorial diversity says that by random combination of 40 functional Vk segments with five Jk segments, the number of possible different k chains that could be made are
200
Since each B cell productively rearranges a single H and L chain allele, it exhibits
allelic exclusion
Primary mRNA for H chain encodes
one VH, one DH, and multiple JH segments.
Somatic recombination occurs
in the progenitor cell as it is becoming a B cell.
Alternative mRNA splicing
is a process by which a B cell can simultaneously synthesize m and d chains.
B cell differentiation begins with the expression of
RAG-1, RAG-2 and TdT.
secrete cytokines such as IL-7 that signal developing B cells to divide and differentiate.
Bone marrow stromal cells
The developmental step that commits a cell to the B lineage is
joining of a DH gene segment to a JH gene segment
Once H chain genes have been productively rearranged and expressed on the pre-B cell membrane, the next event to occur in the cell is
proliferation of the pre-B cells.
f a B cell tumor is monoclonal, it can be differentiated from normal B cells of the same person by its unique membrane Ig
idiotype
If you wanted to check for the presence of memory B cells from your vaccine subjects by taking some of their B cells and re-stimulating them in vitro (outside the body) with antigen, the best place to get some memory cells would be from
blood
VDJ rearrangement on ‘H’ chain occurs in what B cells to produce Heavy chain.
Pro-B cells
VJ rearrangement on ‘L’ chain occurs in what cells to produce Light chain.
Pre-B cells and is arranged in Immture B cells
After the re-arrangement, the B cells are now called
Immature B cells
There are 4 mechanisms in which B cells generate receptor diversity:
Somatic recombination:
VDJ recombination for heavy chain
VJ recombination (No “D” segment) for light chain
Pairing of various light chains with heavy chains
Junctional diversity (nucleotide addition via Tdt)
Somatic hypermutation (single point mutation in antibody idiotype)
During differentiation of this cell into the B-cell, rearrangement of the DNA occurs. This rearrangement aligns __ of the __ V genes with __ of the D genes and __ of the J genes, producing a functional VDJ recombinant gene. Since any of the genes may recombine with any others, this rearrangement has the potential to generate__ V x __D x __J = 6000 different possible combinations.
1 of the many (40) V with 1 of the D and 1 of the J
40 V, 25D, 6 J
cells work closely with macrophages to provide the elegance and complexity of immune function?
Lymphocytes
Major histocompatibility complex antigens are found on all human cells with the exception of what type of cells?
RBCs
Of the MHC genes, which codes for receptors that recognize and react with foreign antigens?
Class II MHC
hat class of MHC receptors is found on the surface of all nucleated cells?
Class I MHC
What is the process by which lymphocyte clones that develop a specificity for self molecules are eliminated or deleted from the pool of genetic diversity?
Immune Tolerance
What leads to the extreme variations in the expression of specific receptors in lymphocytes?
clonal selection
