B Cells 7 Flashcards
what is the difference btwn the primary and secondary response in terms of IgM?
MOST make IgM in primary response, SOME memory B cells make IgM
what is the difference btwn the primary and secondary response in terms of somatic hypermutation?
in primary response, SOME B cells will go to germinal center to undergo somatic hypermutation
in secondary reponse, MOST memory B cells express IgG and undergo further somatic hypermutation
repeated immunization leads to: (3)
- increasing affinity of Abs via SHM and affinity maturation, will re-enter the germinal center each time
- class-switching
- higher levels of MHC II and B7
what is the importance of memory B cells having higher levels of MHC II and B7 than naive B cells? (2)
- helps memory B cells acquire and present Ag more efficiently to T_FH than naive B cells –> more efficient class-switching
- increases Ab production
where do memory B cells go?
they circulate in blood and end up in spleen and LN as they wait for the antigen
what are the 2 types of memory T cells
- T_CM cells –> central memory T cells
- T_EM cells –> effector memory T cells
where are T_CM cells located?
reside in/travel between secondary lymphoid tissue to find their match on APC
what allows T_CM to be reactivated?
rapidly reactivated by second Ag exposure
how do cytokines affect T_CM?
cytokines cause them to differentiate into diff subsets
where are T_EM cells located?
travel to/between tertiary tissues in the periphery
what is the general purpose of T_EM cells?
contribute better to first-line defenses
what happens to memory T cells upon second Ag exposure?
shift right back into effector functions –> no need for strong co-stimulatory signals or cytokines
how do we identify memory T cells?
not as easy to identify like B cells in blood, but can identify in vivo based on immune response
what are the 3 characteristics of memory T cells?
- long-lived
- phenotypically unique
- functionally different
what does it mean for memory T cells to be phenotypically unique?
closer to effector T cells than naive T cells
what does it mean for memory T cells to be functionally different?
less requirements for activation and express a unique set of receptors
still require contact with p:MHC but less sensitive to restimulation
when do memory T cells become effector T cells?
upon reactivation
how does the memory response vary for diff people?
may have diff individual responses but 2nd response is always larger
what is passive immunity?
temporary adaptive immunity due to transfer of immune products (Ab - antiserum) from immune individual –> nonimmune individual
what does the immune system do in passive immunity?
nothing
what is active immunity?
adaptive immunity induced by natural exposure to pathogen or by vaccination
what are 2 examples of passive immunity?
- monoclonal therapy
- breastmilk
when is passive immunity good? 3 examples
provides a preformed antibody which is good when your immune system cannot defend itself:
- immune deficiency
- toxin or venom with immediate threat to life
- exposure to pathogen that can cause death faster than an effective immune response can develop
why is the protection from passive immunization temporary?
does not activate the host’s natural immune response
what happens when Ab are passively transferred to a non-immunized animal?
PREVENTS activation of naive B cells –> no memory
why do we not vaccinate newborns?
Ab they acquired from placenta and breastmilk will kill off the vaccine and don’t activate naive B cells –> then when they get infected, it will be like first response
what is the original antigenic sin?
once we have an effected response, memory cells will be used instead of activating naive cells that target new, unique epitopes
i.e. immune system gets trapped and unable to cause potentially more effective responses
what does active immunization induce?
immunity and memory
what are the 2 ways active immunity can be achieved?
- natural exposure
- artificial (vaccine)
what are vaccines?
use altered, non-dangerous form or component of infectious agent to induce specific immune response with memory
what type of cells are induced by active immunization?
B cells and T cells
what are adjuvants?
chemicals included in vaccines to ENHANCE the immune response
what are 3 ways to enhance the immune response if the Ag is a weak stimulator?
- promote inflammation to recruit more immune cells
- slow down Ag release to promote longer interactions
- adjuvants
what are attenuated vaccines?
virus has multiple mutations that prevent it from causing a productive infection in IMMUNOCOMPETENT humans
have a built-in adjuvant –> PAMPs from virus trigger immune response
what is herd immunity?
when majority of the population is immune to an infectious agent, the pathogen reservoir is reduced due to the low chance of a susceptible individual contacting an infected individual
