Human circulating IFN-γ producing CD4 T cells are enriched in the CD300a⁺ subset.

<p>(A) Flow cytometric analyses for the production of IFN-γ, IL-4 and IL-17 in combination with cell surface expression of CD300a by purified CD4 T cells stimulated with PMA and ionomycin for 4–5 h. The lymphocyte gate was determined according to the forward and side scatter parameters. The CD300a expression was determined for the cytokine producing cells. A representative healthy donor is shown. The bar graph represents the average ± SEM of the percentage of CD300a⁺ cells within each cytokine producing subset. Results are from 15–19 donors. (B) MFI of IFN-γ expression in the cytokine producing memory CD300a⁺ and CD300a⁻ cells. (C) Expression of CXCR3 and CD300a by circulating memory CD4 T cells. Freshly isolated CD4 T cells were labeled with anti-CD4,-CD45RO, -CD300a and -CXCR3. Dot plots are from CD4⁺CD45RO⁺ gated cells. Results from a representative donor are shown from four donors that were analyzed. (D) PBMCs from healthy donors were stimulated overnight with CMV pp65 or TT in the presence of brefeldin A and then analyzed for the production of IFN-γ and IL-2 by memory CD4 T cells (CD4⁺CD45RO⁺). For the cytokine positive cells, the cell surface expression of CD300a was measured. The response of two of the four donors analyzed is shown.