Chapter 1 Pt II Flashcards
Describe positive selection of T cells. Where does it occur? Degree of optimal binding?
Occurs in thymus. Positive selection is screening for T cells that can recognize self-MHC proteins. Failures are apoptosed. Test cells present MHC proteins to T cells. Must LOOSELY bind antigen!
Describe negative selection in T cells. What is the goal?
Goal is to ensure self-tolerance. T cells screened for loose self-MHC binders. If bind too tightly, they are apoptosed.
Which occurs first? Positive or negative selection of T cell?
Positive selection
Describe process of T Cell maturation
HSC’s differentiate into lymphoid progenitor cells. Some cells commit to T cells. Positive and negative selection occur to ensure immunocompetence and self-tolerance. Pool of non-self reactive mature lymphocytes accumulate. Antigen stimulation activates their proliferation and differentiation into effector/memory cells
Describe clonal selection theory
Lots of components:
-T and B cells of several pre-existing specificities before antigen exposure
-Each cell is immunocompetent if it binds/recognizes ONE antigen
-Upon antigen exposure, only cells that bind it are selected
-T and B cells can bind antigen and generate cytokines that cause proliferation
Describe positive and negative selection for B cells
Positive selection: can make antigen receptors
Negative selection: self-reactive
What is clonal deletion?
Elimination of self-reactive T and B cells by apoptosis
Do all B cells differentiate into effector and memory cells?
No. Some stay as they are for future use
Types of APCs?
Dendritic cells, macrophages, and B cells
Function of memory B cells?
Make second exposure stronger and faster
Function of plasma cells?
Produce and secrete antibodies AKA immunoglobulin
Two important aspects of healthy adaptive immune response?
Immunogenicity (ability to recognize antigen)
Reactivity/specificity = bind one at a time
Describe primary immune response lag period, peak levels…etc
Cell proliferation and differentiation upon FIRST antigen exposure
Lag period = 3-6 days
Peak plasma Ab levels = within 10 days (1-2 weeks)
Ab levels decline
Describe secondary immune response lag time, peak Ab levels…etc
Re-exposure to same antigen allows sensitized memory cells to respond within hours
Ab levels peak within 2-3 days at much HIGHER levels than first exposure
Antibody level can remain high for weeks to months
Ab bind at greater affinity
What’s the difference between active and passive immunity?
Active immunity is immunization by induced or natural exposure to antigen. Your body has to do the work to create the antibodies against it.
Passive immunity is immunization by the transfer of Ab from immunized to non-immunized person. Your body does NOT do the work of generating the antibodies
