Humoral Immunity (Habal) Flashcards
(39 cards)
The majority of intracellular pathogens are targeted by what kinds of cells?
T cells
How does the humoral response begin?
It’s launched against extracellular pathogens.
What happens during the humoral response?
B cell activates against a specific antigen. It then undergoes clonal expansion & differentiation. Plasma cells secrete antibodies, which once produced have only a limited shelf-life (although they may persist longer). Memory B cells come along to provide long-lasting immunity.
Genes for heavy chains of antibodies come from which chromosome?
14
Genes for light chains of antibodies come from which chromosomes?
2-kappa & 22-lambda
What is the first Ig to be produced?
IgM
How do you go from IgM to IgG?
Get IgM first as it is genetically encoded in constant region. Post-rearrangement you get class switching - a loop forms, bringing the constant region for IgG or IgA closer to VDJ region, forming the class.
What are the effector mechanisms of the humoral response?
Agglutination (enhances phagocytosis), opsonization, neutralization (blocks toxin binding), inflammation, antibody-dependent cell-mediated cytotoxicity (NK cells), and activation of complement.
What are the 3 subsets of B cells?
Follicular, marginal zone, B-1
Describe follicular B cells.
T-dependent, isotype-switched (IgD & IgM), high-affinity antibodies; long-lived plasma cells. Found in spleen, other lymphoid organs. Respond to protein antigen and helper T cell.
Describe marginal zone B cells.
T-independent, mainly IgM; short-lived plasma cells. Found in white pulp of spleen. Respond to polysaccharides, lipids, nucleic acids.
Describe B1 B cells.
T-independent, mainly IgM; short-lived plasma cells. Found in mucosal tissues, peritoneal cavity. Respond to polysaccharides, lipids, nucleic acids.
What does class switching require?
T cell activation
What is the signal for class switching?
CD40 ligand
What do avidity and affinity of Ig refer to?
Avidity = strength of binding; affinity = specificty
What causes affinity maturation?
Continued exposure to antigens increases affinity over time, causing an increase in antibody specificity.
What are the secondary immune organs?
Lymph nodes, spleen
What is the main job of the red pulp of the spleen?
Filtration - RBC may be attached to opsonins that need to get cleared out.
What are people without spleens susceptible to?
Encapsulated organisms - no marginal zone B cells present to encounter them.
Where does class switching occur in the secondary immune organs?
Medulla
In the generation of antibody diversity, the heavy chain is rearranged first. With this rearrangement of BCR, you will have hypermutation. Define this, and explain its presence/absence in TCR.
Hypermutation - changes to the gene that enhance its specificity, but do not get transmitted to offspring. This is not seen in T cells.
B cells must be what in terms of T cells to class switch?
Be T-dependent.
What happens in Hyper IgM Syndrome?
Results from mutations affecting class switching (rare). Get a decrease in IgG, IgA, and IgE.
What would happen if you had a T Cell that doesn’t express CD40L?
B cell is activated by T cell, but cannot class switch, so you’d only have an IgM response - but this decreases after about a week (not long-lasting). Thus you have a strong initial response that can knock out the organism, but not memory to fight it off at a strengthened initial attack should it come back - susceptible to repeated chronic infections.
