ABSTRACT
Helper T cells selected from KLH-primed lymph node cells under different in vitro conditions were analyzed for the ability to cooperate in secondary hapten-specific antibody responses. It is shown that carrier-specific, MHC-restricted helper T cells selected in low-density cultures cooperate with equal efficiency in either PC-specific or DNP-specific responses. In the presence of both PC-specific and DNP-specific B precursors, however, such T cells are limited to participate in only one helper event in vitro. In contrast, the predominant helper T cell in a second population maintained in high-density lymph node cultures cooperates, presumably through a soluble factor, with multiple B precursors. These properties correspond to those previously described for specific and nonspecific effector functions. The experiments reported here further demonstrate that different B cells respond in vitro to carrier-specific and nonspecific helper signals.
Subject(s)
B-Lymphocytes/immunology , Lymphocyte Cooperation , T-Lymphocytes, Helper-Inducer/immunology , Animals , Antibody-Producing Cells/immunology , Cells, Cultured , Dinitrobenzenes/immunology , Haptens/immunology , Hemocyanins/immunology , Hemolytic Plaque Technique , Lymph Nodes/cytology , Lymphocyte Activation , Mice , Mice, Inbred BALB C , Phosphorylcholine/immunology , Rabbits , T-Lymphocytes, Helper-Inducer/classificationABSTRACT
Clonal expansion of isolated precursors to helper T cells was induced in limiting dilution cultures of keyhole limpet hemocyanin (KLH)-primed F1 hybrid lymph node cells. Progeny of each isolated precursor was tested for helper activity by transfer to independent cultures with hapten-primed B cells of either parental or F1 hybrid origin. The major histocompatibility complex (MHC) restriction specificity of each F1 hybrid helper T clone was determined. To assess the contribution of I-A and I-E subregion-encoded genes to the expression of these restriction elements, helper T cell cultures derived from F1 hybrids between strains with recombinant H-2 haplotypes were analyzed. Parental and unique F1 hybrid MHC determinants that are encoded entirely within the I-A subregion were found to restrict the activity of KLH-specific helper T cells.
Subject(s)
Epitopes , Hemocyanins/immunology , Histocompatibility Antigens Class II/genetics , T-Lymphocytes/immunology , Animals , Cell Separation , Chromosome Mapping , Clone Cells/immunology , Genetic Code , Hybridization, Genetic , Lymph Nodes/immunology , Mice , Mice, Inbred C57BL , RabbitsABSTRACT
Antigen-specific major histocompatibility complex (MHC)-restricted helper T cell precursors were induced to proliferate in cultures of keyhole limpet hemocyanin-primed lymph node cells. Clones of F1 hybrid helper T cells were isolated in limiting-dilution cultures. Each positive culture at a limiting-dilution of lymph node cells gave rise to > 10 helper T cells with a single MHC-restricted specificity. This made it possible to independently assay specific helper activity of isolated clones in secondary cultures with B cells of diverse origin. Different clones with helper activity restricted to either parental or unique F1 hybrid MHC determinants were found to occur at approximately equal frequency. The results are discussed in relation to hybrid Ia specificities and dual-complementing MHC-linked Ir genes.
