Immunologic tolerance to collagen and glycosaminoglycan components of scleral allografts in humans. Evidence for T cell suppression.

Abstract

Unfractionated peripheral blood lymphocytes (PBL) and the T and B cell fractions of PBL from four patients who had received scleral allografts, and fractions from four control subjects were tested in vitro for proliferative responsiveness to collagen and glycosaminoglycan-enriched extracts of allogeneic sclera. None of the unfractionated lymphocyte cultures (patients and controls) were responsive to the scleral extracts. However, B-enriched lymphocyte cultures from one patient and two control subjects did respond to the scleral extracts, although there was considerable individual variation in the magnitudes of these responses (stimulation indices ranging from 1.5 to 11.5). In contrast, the DNA-synthesis response of T cells to scleral extracts was strongly suppressed. Furthermore, T cells pre-exposed for 24 hours to scleral collagen were capable of suppressing B-cell responsiveness to mitogens in autologous mixed lymphocyte cultures. Our findings confirm the lack of apparent adverse immunologic responsiveness to scleral allografts in humans as reported by others. It is possible that immunological tolerance to the scleral allografts is due to a suppressor T-cell mechanism which is triggered by scleral collagen.