Effect of macrophages on elimination of dermal melanin from the dermis.

To facilitate the mobilization of dermal melanin from the skin, we studied the role of macrophages in the elimination of dermal melanin in incontinentia pigmenti. The protein and melanin moieties of mouse-melanoma melanosomes were labeled with 14C and 3H, respectively. Labeled melanosomes were injected intracutaneously into the backs of guinea pigs. Carrageenan, a macrophage toxic agent, showed an inhibitory effect on the degradation and elimination of protein moiety of melanosomes from the dermis, when carrageenan was injected i.p. at the time of inoculation of melanosomes. Delayed-type inflammatory infiltrates in contact dermatitis showed some increase in the elimination of melanin moiety of melanosomes from the dermis.