Electron microscopy of cellular immunity reactions in B-cell deprived rabbits. Thymus derived antigen reactive cells, their micro-environment and progeny in the lymph node.

Three times sublethal total body X-irradiation with thymus shielding--at 14 days' intervals--established an 'isolated T-cell system'. Cellular immunity reactions in draining lymph nodes of rabbits have been analyzed at the ultrastructural level after challenge with horse spleen ferritin, the chemical sensitizer, 2-phenyl-4-ethoxymethylene-5-oxazolone and after skin allografting. A basic pattern of interdigitating cells (IDC) is described as a specific constituent of the thymus-dependent areas of peripheral lymphoid tissue. Their ultrastructural features and presumable functional relationship to the afferent loop of cellular immunity reactions are presented. The differentiation pathway of two T-cell lines is shown and discussed in relation to cellular and thymus-dependent humoral immunity reactions.