IN-SITU CHARACTERIZATION OF THE HUMAN HYALOCYTE

Objective: To provide more definitive evidence regarding the cellular origin of hyalocytes and to establish a basis for their identification in tissue specimens. Methods: Hyalocytes were examined in situ in human eyes from 10 donors (aged 1 to 63 years) with use of a panel of antibodies and lectins directed against determinants associated with leukocytic and nonleukocytic cells. Results: Hyalocytes express the leukocyte-associated antigens CD45, CD11a, and CD64,an antigen expressed constitutively only by monocytes and macrophages. However, they do not react with antibodies against CD68, an antigen that is expressed by virtually all tissue macrophages, or CD 11b and CD 14, antigens that are variably expressed by the monocyte/macrophage lineage. They also react with antibodies against major histocompatibility complex class II antigens and S100, both of which are expressed by a variety of cell types. The lectins Dolichos biflorus, Sambucus nigra, Griffonia simplicifolia, Limax flavus, and Ricinus communis I bind hyalocyte-associated glycoconjugates; no binding was observed with Arachis hypogaea or Glycine max. Conclusions: These results provide strong evidence that hyalocytes belong to the monocyte/macrophage lineage but differ significantly from other tissue macrophages in that they express S100 protein and do not express CD68. This information should provide a basis for the identification of hyalocytes in tissue specimens and an improved understanding of vitreo-retinal pathologic features.