Function of CD44(Pgp-1) homing receptor in human T cell precursors.
T cell precursors migrate from extrathymic hematopoietic tissues and differentiate after encountering the thymic microenvironment. We asked whether human T cell precursors express the CD44(Pgp-1/gp90HR) class of homing receptors that have been implicated in the traffic of hematopoietic cells, such as lymphocyte entry to peripheral lymphoid organs. Flow cytometry and immunoprecipitation studies demonstrate that CD7+34+, CD1-2-3-4-8-14-16-20- cells in bone marrow and thymus, which have been shown to exhibit features of T cell precursors, bear CD44. Immunohistological studies show that clusters of thymocytes in the subcapsular and the inner cortex and most medullary thymocytes are clearly CD44+, whereas the expression of CD44 is selectively downregulated in CD3- and CD3low functionally incompetent cortical thymocytes. The expression of CD44 is not restricted to T cell precursors but also occurs in thymic stroma, which bear a different molecular species of CD44. CD44-specific antibodies exert stimulatory effects on T cell precursors, a process that is dependent on stromal cells. We postulate that CD44 might be an adhesion molecule for precursor homing to thymus and that it participates in cell-to-cell interactions within the thymic environment.
de la Hera
A
A
Basel Institute for Immunology, Switzerland.
Acevedo
A
A
Marston
W
W
Sanchez-Madrid
F
F
D002465:Cell Movement; D006412:Hematopoietic Stem Cells / Q000276:immunology* / Q000502:physiology; D006801:Humans; D008213:Lymphocyte Activation; D016201:Receptors, Lymphocyte Homing / Q000502:physiology*; D013601:T-Lymphocytes / Q000276:immunology* / Q000502:physiology; D013950:Thymus Gland / Q000166:cytology / Q000254:growth & development / Q000276:immunology
D016201:Receptors, Lymphocyte Homing