Search

We have cultivated lymph node microfragments from ß-D-galactosidase (Escherichia coli) primed rabbits and have measured their secondary response directed towards the whole molecule (precipitating antibodies) and to a single determinant (activating antibodies) of the antigen. By decreasing the size of the fragments to 105 cells, we began to observe heterogeneity among identical cultures in terms of positivity of response, antibody specificity, and titers. The affinity of "early" activating antibodies was inversely proportional to the dose of challenge. While no maturation was seen in low and excessive challenge, in all cultures receiving intermediate doses the association constant was raised several orders of magnitude within periods of 20 days. The relevance of these data to the mechanism of affinity selection of antigen-sensitive cells is discussed.

Attempts have been made to provoke a cell-mediated response toward nonimmunogenic antigens by the provision of additional histoincompatibilities on the same cell. An immunological response has been obtained in a skin grafting system, the male-to-female combination in Lewis (L) inbred rats in which non-reaction has always been observed, by sensitizing L female hosts with (F344 x Lewis)F1 male skin grafts. A premature break of the tolerance induced in L rats to F344 antigens was also obtained by sensitizing tolerant recipients with (F344 x Bf)F1 homograft. This hybrid's helper effect, which also occurs when the provision of weak histoincompatibilities is tested, requires the involved antigens to be present on the same cell, and the recipients to be capable of reacting against helping antigens.

SummaryRats concurrently injected with DMBA and UR showed markedly depressed hemagglutinin titers toward HRBC with doses that have no effect when injected alone. The same double treatment with the higher dose failed to prolong the survival time of skin grafts against a weak histocompatibility barrier (F/344 as donor and Lew as recipient).

Une modification de l'immunogenicite des TSTA a ete obtenue par l'hybridation des cellules d'un sarcome de rat (souche Fisher) avec des cellules normales allogeniques. La reponse des animaux syngeniques (immunises avec les heterokaryons) a l'implant de la tumeur fut strictement dependante du scheme d'immunisation.

The reticuloendothelial system (RES) activity by the method of colloidal carbon clearance and the antibody production against heterologous erythrocytes by the method of hemagglutination were studied in hibernating hedgehogs. The organs involved in RES activity and antibody production were histologically studied. The data obtained show that the RES activity in the liver is unaffected in hibernating animals while uptake and localization of carbon particles by the spleen is impaired. The suggested hypothesis is that of a defect in the phagocytic activity of the spleen's macrophages, even if the effects of the disturbance in the handling of hibernating animals is to be considered. The antibody production is inhibited or, at least, reaches no significant values in hibernating hedgehogs. All these facts may be correlated with a general and marked involution of all the lymphoid organs. In fact we can observe a reduced white pulp and involuted follicles in the spleen, a smaller size of the thymus and its substitution by brown fat tissue, and smaller lymphnodes containing brownish material. The results are discussed in relation to the scanty and contradictory data available in the literature.