Expansion of an unusual population of Gr-1+CD3int cells in the lymph nodes and other peripheral organs of mice carrying the lpr gene.

Granulocytes and extrathymic T cells are often activated simultaneously, but they are absolutely separate populations in normal mice. However, some abnormal extrathymic T cells (i.e., CD3int cells) seen in mice carrying the lpr gene were found to express a granulocyte marker, Gr-1. Such mice include MRL-lpr/lpr mice and SCG mice. In parallel with an age-associated increase of IL-2Rbeta(low)CD3int cells which contained double-negative CD4-8- and B220+CD2- cells, Gr-1+CD3int cells increased in number in the lymph nodes and other peripheral organs. In addition to a major population of IL-2Rbeta(low)CD3int cells, there is a small population of IL-2Rbeta(high)CD3int cells which produce normal Fas mRNA and Fas molecule from the lpr gene. It was found that both IL-2Rbeta(low)CD3int and IL-2Rbeta(high)CD3int cell populations contained Gr-1+ cells. IL-2Rbeta(high)CD3int cells tended to contain a higher proportion of Gr-1+ cells than did IL-2Rbeta(low)CD3int cells. More interestingly, Gr-1+CD3int cells expressed a considerable level of mRNA of the mG-CSF receptor, similar to granulocytes. The present study thus yielded further information on an unusual property of abnormally expanding CD3int cells in mice carrying the lpr gene.