Rat NKR-P1+ CD3+ T cells: selective proliferation in interleukin-2, diverse T-cell-receptor-Vbeta repertoire and polarized interferon-gamma expression.

Cells expressing markers of both natural killer and T lymphocytes (NK T cells) in humans and mice express a restricted T-cell receptor (TCR) repertoire, are of CD4- CD8- or CD4+ CD8- phenotype, and upon anti-CD3 stimulation secrete large amounts of interleukin-4 (IL-4) and interferon-gamma (IFN-gamma). NK T cells may be the primary source of IL-4-promoting T helper type 2 (Th2) responses and/or they might be involved in regulating the balance between Th1- and Th2-type immune responses, and may consequently affect susceptibility to autoimmune diseases associated with a skewed Th phenotype. We show that rat NK T cells selectively proliferate to IL-2, and use this fact to analyse cytokine production by NK T cells in two rat strains differentially susceptible to Th1- or Th2-type autoimmune diseases. Analysis by reverse transcription-polymerase chain reaction revealed that, in contrast to mouse, rat NK T cells secrete exclusively IFN-gamma and not IL-4 after anti-CD3 stimulation, and use a wider TCR-Vbeta repertoire, suggesting that rat NK T cells are not essential for the development of Th2-type CD4+ T-cell responses.