To B or not to B: B cells and the Th2-type immune response to helminths

Abstract

Similar T helper (Th)2-type immune responses are generated against different helminth parasites, but the mechanisms that initiate Th2 immunity, and the specific immune components that mediate protection against these parasites, can vary greatly. B cells are increasingly recognized as important during the Th2-type immune response to helminths, and B cell activation might be a target for effective vaccine development. Antibody production is a function of B cells during helminth infection and understanding how polyclonal and antigen-specific antibodies contribute should provide important insights into how protective immunity develops. In addition, B cells might also contribute to the host response against helminths through antibody-independent functions including, antigen presentation, as well as regulatory and effector activity. In this review, we examine the role of B cells during Th2-type immune response to these multicellular parasites.

Figure 1. Protective role for antibodies during challenge infections with H. polygyrus bakeri

Antibodies could potentially provide protective immunity at three points of the parasite life cycle: 1) antibodies present in the intestinal lumen or inflamed mucosal tissue might interfere with parasitic enzymes or other essential processes required for L3 invasion and migration to the sub-mucosa. 2) leukocytes present within the Th2-type granuloma that forms around the invading larva might be activated by the surface bound antibodies IgG or IgE, or antibody (IgM and IgG)-dependent complement activation could result in additional leukocyte infiltration, cytokine production and cytotoxicity. 3) antibodies present within the inflamed mucosal tissue of the small intestine might interfere with essential processes involved in feeding and/or migration of adult worms out of the granuloma and into the intestinal lumen.