Differences in eosinophil and neutrophil chemotactic responses in sowda and generalized form of onchocerciasis

Extravasation of host's leukocytes from blood vessels into inflammatory tissues represents a prerequisite for a subsequent interaction with invaded parasites. The migratory responses of eosinophilic and neutrophilic granulocytes in the polar forms of the filarial infection onchocerciasis were investigated. The hyporeactive, generalized form, the chronic hyperreactive (sowda) form and persons without signs of onchocerciasis from a hypoendemic area for onchocerciasis were compared. Eosinophils from sowda patients responded more strongly to the inflammatory mediator platelet-activating factor (PAF) than those from generalized patients and persons without onchocerciasis. The most significant differences were found between the sowda group and a subgroup of the generalized form with 16-80 microfilariae/mg skin (P<0.05) while patients with low microfilarial density exhibited chemotactic responses similar to the sowda group. In contrast to the strong eosinophil response, neutrophils from sowda patients appeared unreactive to PAF and the tripeptide activator formyl-methionyl-leucyl-phenylalanine (fMLP), thereby differing from both other groups. Laboratory data confirmed a state of hyperreactivity in sowda patients similarly found in generalized patients with low microfilarial density and contrasting with those with a microfilarial density of 16-80 mf/mg. The results revealed an inverse chemotactic responsiveness of eosinophil and neutrophil granulocytes in sowda patients and strengthened the observation of a spectrum of host's responsiveness in onchocerciasis.