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 hum an eyes from 10 donors (aged 1 to 63 years) with use of a panel of ant ibodies and lectins directed against determinants associated with leuk ocytic and nonleukocytic cells. Results: Hyalocytes express the leukoc yte-associated antigens CD45, CD11a, and CD64,an antigen expressed con stitutively only by monocytes and macrophages. However, they do not re act with antibodies against CD68, an antigen that is expressed by virt ually all tissue macrophages, or CD 11b and CD 14, antigens that are v ariably expressed by the monocyte/macrophage lineage. They also react with antibodies against major histocompatibility complex class II anti gens and S100, both of which are expressed by a variety of cell types. The lectins Dolichos biflorus, Sambucus nigra, Griffonia simplicifoli a, Limax flavus, and Ricinus communis I bind hyalocyte-associated glyc oconjugates; no binding was observed with Arachis hypogaea or Glycine max. Conclusions: These results provide strong evidence that hyalocyte s belong to the monocyte/macrophage lineage but differ significantly f rom other tissue macrophages in that they express S100 protein and do not express CD68. This information should provide a basis for the iden tification of hyalocytes in tissue specimens and an improved understan ding of vitreo-retinal pathologic features.