In vitro detection of homocytotropic antibody in lungworm-infected rocky mountain bighorn sheep

Lungworm (Protostrongylus) infections of the Rocky Mountain bighorn sheep induced the appearance of homocytotropic antibodies which could be detected in vitro by their ability to sensitize peripheral polymorphonuclear leucocytes for adherence to the larval cuticle. The elution of this antibody from sensitized cells and the inhibition of the adherence reaction with specific antiserum indicated that the reaction was mediated by a 7Sγ1 immunoglobulin. This immunoglobulin, although transmitted in colostrum, exhibited prolonged persistence at passively sensitized skin test sites. These characteristics are somewhat intermediate to those of human IgE and the 7Sγ1 homocytotropic antibodies of certain other species. The adherence reaction was used to assay the homocytotropic activity of serum from infected animals (washed-cell test). This test was correlated with the ability of serums to sensitize skin for anaphylaxis. The effective hypersensitive response, accounting for both sensitizing and blocking activity, was determined by exposing normal cells to larvae in a medium containing test serum (decomplemented-serum test). This test paralleled inflammatory changes in parasitized animals, monitored by the levels of serum orosomucoid.