CD4 and obesity due to melanocortin 4 receptor deficiency: On the other hand, similar to our obesity study we found a significantly (p = 0.0002) lower proportion of natural killer (NK) cells (i.e., both CD56 bright and dim cells) and higher Tregs (CD4 + CD127low/-CD25 + FoxP3 + cells) (Fig. 7), suggesting a potentially poorer ability to kill cancer cells.