The influence of cyclophosphamide on contact allergy was studied by a method based on the count of cells infiltrating epicutaneous test sites in sensitized guinea pigs. Cyclophosphamide was injected 72 h before sensitization with dinitrochlorobenzene (DNCB). On testing 2 weeks later, marked mononuclear cell infiltration and dramatic increase in the count of basophil polymorphonuclear cells in the upper corium were found, compared to the control group. Cell infiltration in tests performed 1 and 3 weeks after sensitization differed from the reaction after 2 weeks. When cyclophosphamide was given 72 h before testing done 2 weeks after sensitization, both mononuclear and polymorphonuclear counts were found to be greatly reduced. This in vivo method of assessing the degree and composition of cellular infiltration in a contact allergic reaction after different periods of time throws new light on the influence of drugs on a cell-mediated immune response and also the variation in response with time.

The effect of systemically administered corticosteroids on allergic and toxic contact dermatitis in the guinea pig was studied. Dermatitis was provoked with dinitrochlorobenzene (DNCB). The influence of corticosteroids on the sensitization phase was also investigated. The epicutaneous test reactions were assessed with the naked eye, low-power microscopy, and a method based on the counting of infiltrating cells in the upper corium. Prednisolone injected in a dose of 5 mg/kg body weight daily for 4 days starting on the 1st day of sensitization or the 1st day of testing tended to shorten the duration of the contact allergic skin reaction as seen with the naked eye. Microscopically, a decrease in the number of infiltrating basophil granulocytes was found. Prednisolone had no convincing influence on the toxic contact eczematous reaction macroscopically or microscopically. Responses to weakly toxic doses of DNCB tended to fade earlier and to show small displacements of the proportion of granulocytes in the differential count of infiltrating cells compared to controls. The results suggest that prednisolone given systemically influences only slightly the inflammatory cell infiltration in contact dermatitis in the guinea pig.

The damaging effect of long-wave ultraviolet radiation (UVA) on the plasma membranes of cultured human skin fibroblasts was evaluated by cytofluorometry performed after vital staining with fluorescein diacetate. The damage was associated with lipid peroxidation, as shown by accumulation of malondialdehyde and 4-hydroxyalkenals; such accumulation was induced by a UVA dose of only 8 J/cm2. Pretreatment with the effective membrane peroxidation inhibitor alpha-tocopherol (added in the form of alpha-tocopherol succinate) or the singlet oxygen quencher beta-carotene protected the cells from membrane damage. Further, depletion of intracellular glutathione by exposure of the cells to buthionine sulfoximine, an inhibitor of gamma-glutamylcysteine synthetase aggravated the membrane-damaging effects. The results confirm the photodynamic effects of UVA, which presupposes the excitation of endogenous photosensitizer(s) and the production of reactive oxygen species. The present results indicate that this method of detection of alterations in plasma membrane stability may be highly suitable for studying various photobiological phenomena and for use as a model for testing substances that could protect skin from UVA damage. The trypan blue exclusion test proved to be too insensitive to detect these changes.