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In a study of the direct effects of interferon-gamma (IFN-γ) on normal human skin, healthy adult male volunteers received either 3 μg (n = 4) or 30 μg (n=9) of recombinant IFN-γ administered intradermally over 3 days. Biopsies were taken on day 6 and histopathological examination of fixed paraffin-embedded sections from sites which had received 30 μg IFN-γ revealed a moderate perivascular lymphohistiocytic dermal infiltrate with mast cells. Immuno- phenotyping of 5 μm cryostat sections demonstrated that 3 μg IFN-γ induced keratinocyte HLA-DR expression in the absence of any significant infiltrate. More intense keratinocyte HLA-DR expression was produced by 30 μg IFN-γ in all specimens, with HLA-DP concurrently expressed in three biopsies. The ratio of CD4:CD8 cells within the infiltrate was approximately 3:I. CDI+ cells within the epidermis were markedly depleted by 30 μg IFN-γ, while CDI-labelled cells were observed in the dermal perivascular infiltrate. Intradermal IFN-γ induces similar immunopathological changes to those observed in many of the inflammatory dermatoses. [ABSTRACT FROM AUTHOR]

The mononuclear infiltrate found in a variety of inflammatory dermatoses was characterized by a predominance of T helper-inducer lymphocytes (THi), CD4+/CD45RA-/CD45RO+, a population of cells responsible for maintaining and promoting immune reactions. Only small numbers of T-suppressor-inducer lymphocytes (TSi), CD4+/CD45RA+/CD45RO-, cells responsible for inducing CD8 suppressor-effector cells to ‘down regulate’ immune reactions, were seen. The predominance of CD4+ THi lymphocytes was common to all dermatoses studied and suggests a common final pathway in chronic cutaneous inflammation, irrespective of initial causative factors. [ABSTRACT FROM AUTHOR]

Keratinocyte expression of the monocyte/macrophage surface antigens defined by OKMI and OKM5 antibodies (Ortho Diagnostics) was examined using the peroxidase anti-peroxidase immunohistochcmical technique. A range of inflammatory cutaneous disorders were investigated, including lichen planus, psoriasis and atopic dermatitis. Positive suprabasal keratinocyte expression of OKM5 antigen was observed in all disorders, while keratinocyte staining with OKMI antibody was consistently negative. These results provide further evidence that keratinocytes may play an important role in cutaneous immune responses. Furthermore, they are consistent with the recent observation that HLA-DR positive keratinocytes may modulate cutaneous immunological reactions by inducing T-cell unresponsiveness. [ABSTRACT FROM AUTHOR]