The balance of macrophage subsets may be customised at mucosal surfaces

Monoclonal antibodies (mAbs) can discriminate phagocytes (mAb, RFD7+), antigen presenting cells (mAb, RFD1+) and suppressor macrophages (mAbs, RFD1+RFD7+). Here we compare proportions of these subsets in normal mucosa and investigate changes associated with inflammatory disease. Biopsies were obtained from normal and inflamed lung, gut and skin. Cryostat sections were then analysed using mAbs RFD1 and RFD7. At normal mucosal surfaces the RFD1+RFD7+ suppressor cells consistently formed a major population: lung, RFD1+ 11.4%, RFD7+ 43.3%, RFD1+RFD7+ 45.2% and in gut, RFD1+ 37%, RFD7+ 12%, RFD1+RFD7+ 51% while in the skin the three subsets were in relatively equal proportions (RFD1+ 30%, RFD7+ 37%, RFD1+RFD7+ 33%). In inflamed eczematous skin the percentage of RFD1+RFD7+ increased at the expense of RFD1+ and RFD7+ cells whereas in inflamed mucosa the RFD1+RFD7+ population was significantly reduced (asthmatic lung 29%, RFD1+RFD7+, colitis 31% RFD1+RFD7+). In the lung this reduction was concomitant with a rise in RFD1+ cells while in the gut the RFD7+ population increased. It is concluded that balance of macrophage subsets may be customised at mucosal surfaces to sustain suppression of T cell reactivity. Inflammation here is associated with a loss of this suppression.