Humoral Immune Responses (Ch. 7) Flashcards
(34 cards)
Humoral immune response is the primary response against what
Polysaccaride/lipid AG
What Ig’s do Naive B cells express
Igm and IgD
Define T-dependent B-Cell Response
B Cells use THC to perform isotype switching which leads to increased affinity for Ag, memory B Cells, and plasma cells
Define T-Independent B Cell response
No THC used, IgM response with limited affinity
What are the majority of B Cells
Follicular B-2 Cells (reside in follicles of LN) and respond to T-Dependent Response
Define Marginal Zone B Cells
Reside in peripheral region of white pulp in spleen
Respond to blood born Ag
Typically only make IgM
Define B-1 cells
Respond to non-protein Ag in mucosal tissue
Typically only make IgM
Define primary response of B Cells
Time
Peak
Ab Type
Affinity
Usually after 5 days
Small peak
Usually IgM
Lower affinity, more variable
Define secondary B Cell response
Time
Peak
Ab Type
Affinity
Usually before 5 days
Larger peak response
IgG present along with isotype switching
Higher affinity (affinity maturation)
What is the role of macrophages in the subcapsular sinuses of LN
Capture Ag and present o follicles to display to B-Cells
What must happen first for Ag recognition on B Cells
Cross recognition on two or more Ig’s
How can Ag’s bind to multiple Ig’s
They have multiple epitopes
What do B-cells recognize on microbes
C3d by using CR2
What is the purpose of using CR2 to recognize C3d on microbes
Enhances B Cell activation
Where are germinal centers found
In LN follicles
B-cells that have proliferated in the germinal center then go where
To the light zone to be selected with the help of FDC’s
What are follicular Helper T Cells
CD4 cells that have entered the LN Follicles to assist in affintiy maturation
What functions does IgG perform on microbes
Oponosation
What mediates the transfer of maternal IgG to the fetus
FCRN
Define affinity maturation
Allows for greater affinity of Ag to Ab binding if infection is prolonged
Only seen in response to THC dependent protein Ag
Occurs in germinal centers
Caused by point mutation in the V region especially at the Ag binding hypervariable region which involves the switching of Uracil to thymidines
What is the role of FDC within the germinal centers
Used to present Ag to different varieties of B-2 cells which are tested for the highest affinity. Those with lowest affinity are apoptosed
Where are FDC’s present
In the light zone
Memory B-Cells do not excrete what
Ab
Mutations in affinity maturation are usually clustered where
In the Ag-binding regions
