Monoclonal antibodies (mAb) raised to the cuticule surface of second-stage juveniles (J2) of the nematode Heterodera cajani were partially characterized by immunofluorescence and Western blot analysis. Five antigens with relative molecular weights (M(r)) 55, 80, 110, 180 and 210 kDa were identified with six mAb. Pasteuria spores, originating from the same population of H. cajani to which the antibodies were raised, were tested for their ability to attach to J2, which had been pretreated with each of the mAb. Monoclonal antibody HC/129 was found to reduce spore attachment by 42%, whereas HC/145 increased spore attachment by 124%. This is the first record of an antibody binding to the cuticle and increasing spore attachment, and suggests that components of the cuticle involved in inhibiting spore attachment may be masking the Pasteuria receptor present on the cuticle.