Characterization of host responder types after a single Cooperia oncophorainfection: kinetics of the systemic immune response

After primary infection with 100 000 third stage larvae of the intestinal n ematode Cooperia oncophora in 3-month-old calves, a high variability in egg output and worm counts is observed. Based on this variability, infected an imals can be divided in different responder types. The three major phenotyp es can be classified as high, intermediate and low responder animals. We in vestigated whether calves classified into different responder types show di fferent immune responses during infection. Peripheral blood eosinophil coun ts and flow cytometric analysis of different lymphocyte subsets of the bloo d did not reveal major differences between infected and control animals, no r between responder types. However the levels of Cooperia-specific immunogl obulin (Ig)G1 and IgA during primary infection were significantly higher in intermediate responders than in low responders. In the intermediate respon ders, isotype specific responses were negatively correlated with parasitolo gical parameters expressing worm expulsion and influence on worm fecundity. Total serum IgE levels were elevated in most of the infected animals. A qu antitative positive relationship between worm counts and total serum IgE le vels was observed. Based on the observed correlations, we propose a role fo r the humoral response against the maintenance of the infection in the gut.