OKT 6-positive cells: their demonstration in human thymus, and the effect of fixation on the immunoperoxidase reaction.

Human thymocytes at an intermediate stage of differentiation were demonstrated in situ in tissue sections of thymus using the mouse monoclonal antibody OKT 6 THY (Ortho Immunobiology Ltd, Raritan, NJ) and the immunoperoxidase technique. These cells were found to reside mainly within the thymic cortex. The effects of on-slide fixation on the ease of demonstration of the antigen involved were assessed. The choice of fixative was found to have a marked effect, acetone and paraformaldehyde producing the most satisfactory results.