Suppressor activity of Mac1⁺ cells toward the in vitro alloresponse. MACS-separated Mac1⁺ and Mac1- or unseparated cell fractions were cocultured in C3H × AKR (MitC) MLR. Results are expressed as percent suppression of the spontaneous proliferative activity that was detected in the absence of additional cell populations. Bars represent means ± SEs of 12 individual animals tested in 3 independent identically designed experiments. (^*P < .05 for comparison between groups, as tested by Kruskal-Wallis multiple comparison Z-test).