B cell activation

[thestrokes14]

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Can someone clarify how B cells are activated (so as to produce plasma and B memory cells). Is it true that some B cells are directly activated by a foreign antigen, while some are activated by macrophages that have engulfed a foreign particle?

Any help is appreciated!

 

[RogueUnicorn]

IIRC, the type of antigen determines whether or not a T-cell is needed to help activate the B cell. Larger antigens, like bacteria, with many epitopes on the surface are less likely to require T-cell help, I believe. This stuff is a bit advanced for the MCAT though.

 

[PeterPesto]

B Cells are activated by Helper T Cells. For instance, a macrophage or dendritic cell, which has engulfed an antigen will present the antigen (antigenic determinant) to a helper T cell.

These cells have special MHC molecules which bind intracellular antigens (e.g. intracellular bacteria, viruses), and allow the antigen to be presented on its surface. Once presented on its surface, the helper T cell recognizes the antigen, and secretes chemicals such as interleukines (messengers) that activate B cells and T cells. This only applies to intracellular infection.

 

[PiBond]

Can someone clarify how B cells are activated (so as to produce plasma and B memory cells). Is it true that some B cells are directly activated by a foreign antigen, while some are activated by macrophages that have engulfed a foreign particle?

Any help is appreciated!

Remember that B cells place a copy of the antibody they are able to produce on the surface of their cell.

When a B cell runs into an antigen that it recognizes via its cell surface receptor it becomes activated and also immediately begins to produce daughter cells. All of the daughter cells are clonal copies of the original B cell.

Of course, "complete" activation does not result simply by a B cell bumping into its antigen. We need help from T helper cells. The rest of the story is beyond the scope of the MCAT.

Does that help?

 

[Charles_Carmichael]

This forum is for MCAT-related questions, not homework help. This is beyond the scope of the MCAT. Closing thread.