T cell help mechanisms in the in vitro antibody response: the role of linked and non-linked recognition interactions.

Mechanisms by which T and B lymphocytes co-operate in the in vitro secondary antibody response to trinitrophenyl (TNP)-conjugated soluble protein antigens were investigated. The generation of antibody responses was analyzed when haptenic and carrier determinants were either linked or non-linked. Ability to co-operate through each of these mechanisms was influenced by the experimental conditions employed, particularly the mode of preparation of the T cells and the antigen concentration used. Nylon wool filtration of T cells may deplete a T helper population involved in non-linked recognition interactions. High antigen concentrations favour the non-linked form of interaction whereas low antigen concentrations favour linked recognition interaction. These data suggest that at least two distinct co-operative mechanisms co-exist. However, experimental conditions can be defined under which either one mechanism predominates or where more than one mechanism is relevant.