3.2.4 - B Cells & The Humoral Response

Tuesday 23rd January ‘24

What is the humoral response?

• Humoral response takes place in blood and tissue fluid (*learn more 3.3.4.2*) of the body.

• Involves antibodies (soluble in blood and tissue fluid) which are produced by B cells.

• Each type of B cell can produce specific antibody (we have each type from birth).

How does the primary humoral response happen?

• In bone morrow, immature B cells divide by mitosis.

• These produce antibody receptors which are then put on cell-surface membrane.

• Mature B cells circulate and concentrate in liver and spleen (producing mature B cells each with a different antibody receptor).

• Only one of these B ceks has an antivody receptor specific to shape of antigen entered the body.

• Helper T cells (previously attached to APC) attach to B cells, activating them. The selected B cell divides by mitosis (clonal selection). Some of the daughter cells develop into plasma cells, others into memory cells.

• Plasma cells secrete antibodies into blood plasma that specifically combine with antigen that’s entered the body.

  • Small life span but can make up to 2000 antibodies per second.

  • Lead to destruction of pathogen.

How does the secondary humoral response happen?

• Antigen enters body.

• Memory cells produced respond and divide to form more plasma cells which secrete antibodies.

• Response faster as many memory cells in body.

  • Live longer than plasma cells.

  • Don’t directly produce antibodies, but circulate the body.

  • If they encounter the same antigen again, they divide rapidly and develop into new plasma cells (producing antibodies) and more memory cells (circulating the body).