THE EFFECT OF INTRADERMAL INJECTION OF GM-CSF AND TNF-ALPHA ON THE ACCUMULATION OF DENDRITIC CELLS IN OVINE SKIN

Intradermal recombinant ovine (rev) GM-CSF was associated with the acc umulation over 5 days of MHC Class-II+ dendritic cells at the injectio n site, as well as increased numbers of neutrophils, eosinophils and l ymphocytes when compared to control injection sites receiving heat-ina ctivated cytokines. Most of the dendritic cells were adjacent to the e pidermis and dermal structures such as hair follicles, sweat glands an d blood vessels. Fewer than 10% of the accumulating MHC Class-II+ dend ritic cells expressed the CD1 antigen and none expressed detectable CD 11b or CD11c antigens. They did not appear to be proliferating. Inject ion of rov TNF-alpha was associated with an increase in MHC Class-IIdendritic cells that was significant only in the epidermis and only at 2 days following the first of four daily injections. Increased number s of neutrophils and lymphocytes, but not eosinophils, were also recor ded. Injection of rov TNF-alpha together with rov GM-CSF enhanced the accumulation of the MHC Class-II+, CD1(+) subpopulation of dendritic c ells compared to either cytokine alone. GM-CSF in particular is involv ed in an in vivo pathway supporting the accumulation of predominantly MHC Class-II+ CD1(-) dendritic cells which are a minor population in u nchallenged skin.