Humoral Immunity Flashcards

Question

Location and Mechanism of Class Switching

Answer 1

The class switching occurs in the lymph nodes when B cells proliferate and mature It is a gradual process, and can even happen in periphery Constant region genes are lined up and must switch in order, and cuts out the preceding class to make the next class, and once cut out cannot switch back to that class B cells cannot secrete Ig’s until mature

Answer 2

``` Non-protein Polymeric antigens (polysaccharides, nucleic acids) and B cell mitogens can directly stimulate B cell activation, but without T help little or no Ig class switching, affinity maturation, or B cell memory responses are generated. (mostly IgM class responses). Pure polysaccharide vaccines are poorly effective because little IgG is stimulated by the T-independent immunogen Protein-polysaccharide conjugate vaccines provide T and B cell epitopes for good IgG and memory responses ``` C3D – degradation product, and B cells have CD21 which is a receptor for CD3, so if B cell simultaneously binds microbe and C3D, it physically cross links the molecules and causes clustering and signaling cascades for Ab production Some examples for microbial patterns, if Ab binds target and PAMPs bind TLRs these two signals can drive T cell independent Ab production

Answer 3

``` T cell dependent are best long term immune response because mediates so many things IgG is the highest in concentration, more important functions, etc. and to be able to switch is from T cell signal from protein stimulus (protein Ag) Many of the important Ag on the surfaces are carbohydrates, and since T cells ONLY respond to proteins, it cannot respond to these Without T cell signal, B cells cannot get activated and will only make IgM Polysaccharide vaccines with covalent protein bound and peptide determinant – provide T and B cell determinant and Ig class switching Can make Ab responses to non-proteins called T independent responses, but little affinity maturation, class switching, or B cell memory cell production occurring ```

Answer 4

``` The Ig heavy chain class switching is driven by T cells and cytokines B cell can change which heavy chain it expresses and all depends on which cytokines it being secreted by the T cell There is no changing of the light chain type or class Why would you switch the conservative area but not the Ag specific area? To make protective response to a specific challenge; want to conserve specificity binding site Order of Switching: IgM, IgG, IgE, IgA ```

Answer 5

Antibody secretion is sustained by plasma cells in medullary cords of lymph nodes (2-4 day lifetime) and in bone marrow (months to years after initial response) Possible replenishment by memory cell differentiation B memory cells recirculate through B cell zones of secondary lymphoid tissues 100X increase in frequency of antigen-specific B cells after primary response Follicular dendritic cells (FDC) may serve as a reservoir of antigen (trapped as immune complexes bound to FDC membrane FcR and CR) for long term re-stimulation of memory cells T and B cell memory are maintained for life

Answer 6

First time exposed to Ag: primary response and then in future is secondary Timing and type of Ab is different Lag: exposure to development of Ab levels – 1-2 weeks/5-10 days Secondary response: 1-3 days in circulating Ab levels Peak level is bigger in secondary IgM is first, and the longer the response occurs then switching occurs Repeated exposure: go to predominate class Affinity maturation: Ab produced early have low affinity, but Ab accumulates during another exposure, the higher the affinity Prime the immune response with immunizations

Answer 7

Purified antigen-specific antibodies are used for very sensitive and specific lab detection and quantitation of Infectious agents Drugs, hormones, toxins, plasma proteins Tumor antigens Tissue Transplantation antigens, blood groups Purified antigens can be used to detect specific antibody responses in plasma as evidence of present or past immune responses

Answer 8

One antibody can bind to 2 different immunogens if they share a common epitope Patient serum (polyclonal mixture of antibodies) may show a false-positive test for specific antibody activity to a microbe because of cross-reactivity of an antibody to a shared immunogen between different microbes. Make heterogeous response and making many Ab; may have two viruses that share some structures, but also have unique proteins; if you make an immune response to one, you will also make Ab that can be used for both viruses and get cross reactions and won’t be able to detect specific virus alone Influenza: has many types, lots of shared molecules between organisms

Answer 9

“Titer”= reciprocal of highest dilution of serum that gives a physical reaction with specific antigen in a laboratory test In an immunocompetent person, antigen X exposure causes an increase in specific antibody “titer” to X (anti-X) over the course of an illness Elevated antigen-specific plasma IgM levels (titers) indicate recent antigen exposure; short half life so indicates recent exposure if present Elevated antigen-specific plasma IgG levels (titers) indicate current or past antigen exposure; long half life and indicates memory Ab and from long time ago exposure

Humoral Immunity Flashcards

(33 cards)