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The rossette inhibition test, an established test for determining the immunosuppressive potential of antilymphocyte serum, has been applied to the serum of sheep after mating. The rosette inhibition titre was much higher (12--26) in 7 sheep which were fertilized and remained pregnant for up to 21 days than in 5 sterile ewes mated with intact rams (8--10). The difference was apparent by 24 h after mating. One ewe had high titres for 6 days after mating but these then dropped and she returned to oestrus; early embryonic loss was suspected. Another ewe which returned to oestrus had consistently low titres. The results indicate that the rosette inhibition test can be used to detect fertilization, early embryonic death and continued pregnancy in sheep.

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Summary The systemic effect of ultraviolet (UV) irradiation on delayed type hypersensitivity (DTH), contact hypersensitivity (CHS) and allograft rejection was investigated in BALB/c mice which had been exposed to a single 1 h treatment with UV radiation (27 kJ/m^) from FS40 sunlamps (60% UVB). After UV irradiation (3-5 days), mice were treated on an unirradiated site with either a subcutaneous injection of allogeneic spleen cells or a topical application of the contact scnsitizer oxazolone (OX). The DTH response to allogeneic cells and the CHS response to OX elicited 6 days afterimmunization were significantly lower in UV-treated mice than in normal mice. Spleen cells from these animals were transferred intravenously into X-irradiated (600R) recipients which were immediately challenged with antigen and the DTH or CHS response elicited was determined 24 h later. Recipients of equal numbers ofcells from sensitized and normal animals (6X10^ from each donor) exhibited positive DTH or CHS responses to the antigen used to sensitize the donor. In contrast, recipients of equal numbers ofcells from animals sensitized and UV suppressed to the same antigen showed a suppressed DTH or CHS response. This suppression was antigen-specific. Treatment ofcells from UV suppressed animals, prior to transf^er, with complement and cytotoxic anti-Lyt 2 or anti-Thy 12 monoclonal antibodies abrogated the suppressive ability of these cells, in contrast to cytotoxic treatment with anti-L3T4 or anti-Lyt 1 monoclonal antibodies which had no significant effeet. The suppressor cells therefore had the phenotype Thy 12 + , Lyt 2 + , L3T4"'. Lyt l^. In a separate series of experiments BALB/c miee, either untreated or given I h of U V irradiation 3-5 days previously, were given a heart or skin allograft from a C3H/He donor. The primarily vascularized cardiac ailografts survived significantly longer in UV-irradiated than in normal recipients (median survival time 13 daysvs 10 days, /'=0 035), but the survival of C3H/He skin ailografts was unaltered in UV mice. No identification of suppressor populations was carried out in the heart allograft recipients. These experiments provide the basis for investigations ofthe possible role of UV-induced antigen-specific suppressor cells in modulating responses to alloantigens.

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Keratinc cyte cell culture has been studied by a large number of investigators, resulting in an extensive body of often contradictory literature. The advantages and disadvantages of the two major techniques, explain and disaggregated culture, will be examined, followed by a critical evaluation of the major technical variables. Suggested standardized methods for both explant and disaggregated culture, and the indications for the use of each, will be proposed. Finally, further directions for basic research will be suggested in order to improve this useful tcol.