Complement receptors on guinea pig epidermal Langerhans cells.

A population of guinea pig epidermal cells possessed the ability to form rosettes with IgM antibody-sensitized sheep erythrocytes coated with purified human C3b (SEAIgMC1-), but not with intermediates carrying C1, C4, or C2. This population of rosette-forming epidermal cells was identified as Langerhans cells (LC) ultrastructurally and by LC depletion and enrichment studies. In addition, these cells were able to bind fluid phase C3b, which inhibited any subsequent SEAIgMC1-3b rosette formation. Rosette formation was also inhibited after SEAIgMC1-3b pretreatment with beta 1H and C3b-inactivator. LC were shown to possess trypsin-resistant C3b and Fc receptors, and unlike the temperature-independent nature of LC Fc-rosette formation, the ability of LC to form C3 rosettes was a temperature-dependent process. The finding of C3b receptors on the surface of guinea pig epidermal LC supports the concept that they are of the phagocytic monocyte-macrophage family.