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lymphocytes

 

Definition: White blood cells that are responsible for humoral and cellular immunity.

Types

-  T lymphocytes
-  B lymphocytes

Features

-  lymphocyte migration

References

-  O'Garra A, Arai N. The molecular basis of T helper 1 and T helper 2 cell differentiation. Trends Cell Biol. 2000 Dec;10(12):542-50. PMID: #11121747#


Diapedesis of lymphocytes - FRom Biocarta

Maturation of T and B Lymphocytes. -

From N Engl J Med. 1995 Aug 17;333(7):431-40

Progenitor cells derived from hematopoietic stem cells enter the thymus and undergo several stages of maturation, during which the and chains of the T-cell receptor and the five chains of CD3 are expressed.1 Immature T cells transiently express both CD4 and CD8. The interaction of CD4 with MHC class II molecules or of CD8 with MHC class I molecules on thymic stromal cells is instrumental in determining whether the cells will survive to become mature CD4+ or CD8+ T cells.

Lymphoid progenitor B cells interact with neighboring stromal cells in bone marrow to give rise to a population of pre-B cells. Pre-B cells first express µ heavy chains in their cytoplasm and then an IgM-receptor complex. The transmembrane immunoglobulin and signal-transduction unit, which is analogous to T-cell CD3, is also expressed.4 The pre -B cells subsequently express and light chains to become IgM-bearing mature B cells committed to an antibody specificity that they and their mature plasma-cell progeny will produce.5 On leaving the bone marrow, IgM-bearing B cells acquire surface IgD. These mature B cells can respond positively to an antigen and to help from CD4 T cells by undergoing proliferation and differentiation; ultimately, they secrete antibody of all the immunoglobulin classes.

The red bars indicate where maturation is blocked in autosomal recessive and X-linked severe combined immunodeficiency, X-linked agammaglobulinemia, MHC class I and II deficiencies, and the hyper-IgM syndrome.



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