Humoral response

Where do B cells mature?

Bone marrow

Where do B cells spread to in the body?

Concentrated on the lymph nodes and spleen

What are BCRs

B cell receptors

Describe the structure of the BCRs

Similar to antibody structure

Specific to one antigen

What are B cell clones?

When a small number of B cells have the same BCRS, they are genetically identical

What are the 3 stages of humoral response?

1. antigen presentation
2. clonal selection
3. clonal expansion

Describe stage 1, antigen presentation

Phagocyte engulfs pathogens and presents the antigen on their MHC, becoming an APC (antigen presenting cell)

How else can B cells be activated?

By responding (binding to) smaller, soluble antigens which float freely in the blood

Describe stage 2, clonal selection

B cells have BCRs which are complementary to the pathogenic antigen

These are the clones that are selected for replication

Describe stage 3, clonal expansion

B cell clones divide via mitosis to produce larger clones

So there are large numbers of B lymphocytes produced over a few weeks

How are the plasma cells formed?

Some B lymphocytes differentiate into plasma cells

T helper cells release IL-2 which stimulates B cells to divide and produce plasma cells

What do plasma cells secrete?

Antibody molecules

What is the speed of the response to a newly encountered pathogen

slow

What happens to other B cells that don’t differentiate into plasma?

become memory cells which circulate in the blood for a long time