Hapten competition and the nature of cell-cooperation in the antibody response

Abstract

Abstract It has been known for many years that the secondary response to a hapten requires the hapten to be conjugated to the same carrier molecule which was used for the primary sensitization (the ‘carrier effect’). Thus it came to be suspected that the specificity of cellular recognition was somehow more rigorous than the specificity of the secreted antibodies. At first, it was supposed that the cellular recognition site must take in a part of the carrier molecule (‘local environment hypothesis’), but this led to the proposition that the molecule serving the purpose of recognition could not be the same as the molecule which was subsequently secreted—which is a serious difficulty for any selective theory of antibody formation. An alternative to the local environment hypothesis seems firmly based now that it is realized that the carrier effect depends on the recognition of two different epitopes on the same antigen molecule by two different cells (Mitchison 1968a; Rajewsky, Schirrmacher, Nase & Jerne 1969; Mitchison, Rajewsky & Taylor 1969). These cells have recently become identified with two varieties of lymphocytes, the characteristics of which have been succinctly reviewed by Roitt, Greaves, Torrigiani, Playfair & Brostoff (1969). The ‘marrow-derived’ or ‘B-lymphocytes’ develop independent of the thymus. They are precursors of the cells which release serum antibody but probably play no essential part in cell-mediated immunity. The ‘thymus-derived’ or ‘T-lymphocytes’, on the other hand, require the presence of the thymus for their maturation, do not develop into antibody-forming cells, but do play an essential role in cell-mediated immune responses. Although T-lymphocytes do not themselves secrete antibody they play an important part in primary antibody responses by cooperating with B-lymphocytes (see Transplantation Reviews 1, 1969).