Re: Are B lymphocytes pre-T lymphocytes?

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B cells and T cells are the two cell types that comprise the adaptive immune system. B cells (originally named because they were found in the Bursa of Fabricius in birds) are the cells that produce immunoglobulin, otherwise known as antibodies. These cells develop from precursors in the bone marrow and are then released into the circulation as immature B cells. B cells then mature in the periphery. B cells have molecules on their surface that mark them as B cells, such as immunoglobulin, CD19 and Ig alpha and Ig beta.

T cells on the other hand, migrate as precursors from bone marrow into the thymus (which is located near the heart). Once in the thymus, T cells are educated to recognize self and nonself (they undergo something known as positive and negative selection, where they are trained to see foreign antigens but be tolerant to self antigens). T cells are marked on their cell surfaces by the T cell receptor, signaling CD3 molecules, and usually either the coreceptors CD4 or CD8 (you may have heard of CD4+ T cells in the context of AIDS patients). CD4 T cells provide help to B cells (so they can produce antibody) and CD8 T cells (so they can kill virally infected cells).

So, no, B cells are not pre-T cells, but a different cell type entirely that has the function of producing antibody.

I hope this helps!
Ingrid Dodge
MadScientist

Some good introductory immunology textbooks:
1) Immunobiology by Charles Janeway, Jr.
2) Immunology by Janis Kuby
3) Cellular and Molecular Immunology by Abbas, Lichtman and Pober