Abomasal lymph node responses to Haemonchus contortus intestinal antigens established in kid goats by infection or immunization with intestinal antigens

Abstract

Immune responses to Haemonchus contortus intestinal antigens were evaluated using abomasal lymph node (ALN) lymphocytes from kid goats protected against challenge infection by immunization with parasite intestinal antigen, and from kids that were challenged after immunization with ovalbumin. ALN lymphocytes from the intestinal antigen-immunized group produced significantly higher antibody levels against intestinal antigens than the ovalbumin group, supporting the theory that immunization contributed to that ALN response. In contrast, intestinal lysates and membrane enriched preparations from intestinal cells stimulated significant proliferation of ALN lymphocytes in both groups. The proliferation was antigen-dependent, since intestinal antigens failed to stimulate proliferation in ALN lymphocytes from unimmunized and uninfected kids. For both the intestinal antigen and ovalbumin immunized groups, CD4+ T lymphocytes predominated in ALN lymphocytes that were stimulated to proliferate by intestinal antigens. The results indicate that H. contortus infection alone can induce ALN lymphocyte responses to intestinal antigens. In contrast to ALN lymphocyte responses, serum antibody against intestinal antigens was generally low to undetectable in ovalbumin-immunized kids following infection. Abomasal mucus from an H. contortus infected lamb was probed with a monoclonal antibody that binds to a periodate sensitive determinant on numerous H. contortus intestinal membrane and secreted proteins. Numerous bands of reactivity were detected, indicating that multiple parasite intestinal antigens were released into abomasal mucus during infection. The results, challenge the general concept that H. contortus intestinal antigens are 'hidden' from the host immune system during an infection. On the contrary, parasite intestinal proteins may be relatively abundant antigens presented to the host during infection. In addition, ALN T lymphocytes appear to provide a more sensitive measure than serum antibody to detect presentation of these antigens to the host immune system.