Down-regulation followed by re-expression of equine CD4 molecules in response to phorbol myristate acetate.
The regulatory effects of phorbol myristate acetate (PMA) on the expression of the CD4 molecule on horse T cells were investigated. On both peripheral blood lymphocytes and thymocytes, PMA resulted in a rapid and transient down-regulation of equine CD4 expression, but had no such effect on the surface expression of equine CD5, CD8 or major histocompatibility complex (MHC) class I and class II molecules. Over 75% of the surface CD4 molecules per cell were lost after a 4 h exposure to PMA at 37 degrees C. The regulation of equine CD4 expression induced by PMA was temperature dependent and reversible. The PMA-mediated loss of CD4 expression was inhibited at 4 degrees C. After 24 h of exposure to PMA, CD4 molecules were re-expressed on the cell surface, even in the continued presence of PMA. These findings demonstrate that equine CD4+ T cells undergo alterations in CD4 expression in response to PMA, and suggest that the equine homolog of the CD4 molecule is regulated by PMA in a similar manner to the human CD4 molecule.
Zhang
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CH
Cornell Equine Genetics Center, James A. Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853.
Grünig
G
G
Davis
W
W
Antczak
D F
DF
D000818:Animals; D015704:CD4 Antigens / Q000378:metabolism*; D015496:CD4-Positive T-Lymphocytes / Q000187:drug effects*; D015536:Down-Regulation / Q000187:drug effects; D005434:Flow Cytometry / Q000662:veterinary; D006736:Horses / Q000276:immunology*; D008213:Lymphocyte Activation / Q000187:drug effects; D013696:Temperature; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
D015704:CD4 Antigens; D013755:Tetradecanoylphorbol Acetate