The worm and the protozoa: Stereotyped responses or distinct antigens?

Abstract

Studies of parasitic diseases have provided the best in vivo correlates of the division of CD4+ helper T cells into distinct functional phenotypes, designated T_HI and T_H2, that mediate the balanced regulation of cellular and humoral immunity. In this article, Steven Reiner and Richard Locksley focus on why parasitic infections tend to generate such clearly polarized responses and emphasize that early events that mediate maturation signals towards T_H1- or T_H2-effector and memory cells remain incompletely defined. Effective vaccination that seeks to mold the developing immune response will need to consider the role of interleukins and various cell-surface molecules that have been identified, thus far, to influence CD4 subset differentiation.