CYTOKINE MESSENGER-RNA EXPRESSION IN SKIN IN RESPONSE TO ECTOPARASITEINFECTION

Cellular infiltration and local cytokine mRNA levels were examined dur ing the first 48 h of infection of skin by larvae of the sheep blowfly Lucilia cuprina. At the cellular level the response involved a dramat ic influx of leucocytes (CD45(+) cells). Among these infiltrating cell s were large numbers of granulocytes, including neutrophils and eosino phils, as well as macrophage-like cells and lymphocytes. Many of the l ymphocytes expressed cell surface markers characteristic of T cells in cluding CD4, CD8 and the gamma delta TCR. The numbers of each of these cell types increased progressively as infection continued so that by 48h the lesions were densely populated. Expression of mRNA for IL-6 co uld be detected by Northern blot analysis while mRNA for other inflamm atory cytokines including IL-1 alpha, IL-1 beta, IL-8 and TNF alpha wa s detected using the polymerase chain reaction. Coincident with the in flux of granulocytes and other cells there was an increase in the leve l of mRNA for the cytokines IL-1 alpha, IL-1 beta, IL-6 and IL-8. In t he skin of the sheep there appeared to be constitutive expression of m essage for the cytokines IL-1 beta, IL-6 and TNF alpha, with the level of the latter not found to increase during the 48 h of infection exam ined. In situ hybridization n was used to determine the location of IL -6 and TNF alpha mRNA within resting and infected skin. During infecti on, fibroblasts, macrophage-like cells and endothelium appeared to pro duce high levels of IL-6 mRNA. Expression of the T cell dependent cyto kines IL-2 and IFN-gamma but not IL-4, increased in expression as time progressed and the population of infiltrating cells, including T cell s, expanded.