Search

The results presented in this paper demonstrate that a mouse IgM monoclonal antibody (T-80) recognizes an antigen on cells of the T-lymphocyte lineage of sheep. However, this antibody does not identify all T cells, as 10-20% of thymocytes and some peripheral-blood T cells are negative. T-80- thymocytes reside in the medulla. The majority of cortical thymocytes are T-80+ and classified as dull cells on the basis of antigen density per cell as measured by flow microfluorometry. In contrast, T-80+ cells in the periphery can be categorized into two populations, i.e., dull cells and bright cells. Suggestive evidence was obtained that bright T-80+ cells are fast recirculating T cells, whereas dull ceils are sessile or less easily mobilizable T cells in the periphery. In foetal environment, over 90% of thymocytes and approximately 5% of spleen cells are T-80+ at 54 days of gestation (gestation period = 150 days), which may indicate that T-cell emigration from the thymus commences well before mid-gestation in sheep. [ABSTRACT FROM AUTHOR]

Two distinct murine B-cell differentiation factors, designated B 151 -TRY 1 and B 151-TRF2, were described originally as B151 K12 T-cell hybridoma-derived lymphokines that induce immunoglobulin (Ig) secretion by antigen-activated B cells and unstimulated B cells, respectively. In the present study, we found that a highly purified B1 51-TRF1 fraction prepared by reversed-phase high-performance liquid chromatography (RP-H PLC) also has the ability to cause a polyclonal differentiation of unstimulated B cells into IgM-secreting cells in the apparent absence of co- stimulant. The activity of the B151-TRF1 fraction but not the B151-TRF2 fraction on unstimulated B cells was markedly inhibited by addition of a monoclonal antibody (mAb) specific for the B151- TRF 1/IL-S to the culture. To determine whether 8151 -TRF 1/IL-S and 8151 -TRF2 act on distinct populations among unstimulated B cells, the responsiveness of neonatal B cells and adult B cells that had been fractionated by Percoll density gradient centrifugation was assessed. B15 l-TRFI/IL-5 predominantly acted on lower density B cells, which appeared around 3 weeks after birth in the spleen. In contrast, B151-TRF2 could activate both lower and higher density B cells almost equally and B 151 -TRF2-responsive B cells were already present by 1 week of age. Thus, these results suggest that B151-TRFI/IL-5 and B151-TRF2 act on distinct subpopulations among antigen-unprimed normal B cells to induce IgM-secreting cells. [ABSTRACT FROM AUTHOR]

Quantitative studies on B cells require a direct assay for antibody-forming cell (AFC) progenitor function, in which the number of AFC produced bears a simple, linear arithmetic relationship to the number of progenitors present. This might be expected under conditions where helper T-cell and accessory cell requirements are by-passed, or provided in excess. This possibility has been tested using as antigen the hapten NIP (4-hydroxy-3-iodo-5-nitrophenylacetic acid) on the carrier POL (polymerized bacterial flagellin), in adoptive transfer of normal and nude mouse spleen cells to irradiated recipients, and in cell culture. Primary and secondary IgM responses to this antigen are 'T cell-independent'. The secondary IgG response is T cell-dependent but this function can be provided by 'carrier- primed' irradiated recipients. However in no case did the cell dose response curve show a linear, arithmetic relationship between cells transferred or cultured, and AFC produced. If less than 10 × 106 cells were adoptively transferred or cultured, a sigmoid curve was obtained, approximately linear with a slope of around 1.6 on a log-log scale. In adoptive transfer, a plateau was then seen above 10 × 106 cells, followed by a second sharp rise beginning around 15 × 106 cells. Addition of irradiated spleen cells as 'fillers' to maintain cell numbers constant produced a linear (arithmetic scale) dose response curve for the primary IgM responses, both adoptive and in culture. Lipopolysaccharide injection of recipients also produced linear regions in the adoptive transfer system. These techniques provide more direct, quantitative assay systems for the primary IgM responses to this antigen. However, arithmetic linear cell dose response curves were still not obtained for the secondary IgG responses, using irradiated filler cells. [ABSTRACT FROM AUTHOR]

Comparative study of two T-cell subpopulations, killers and MIF producers, immune to H-2 antigens, was performed using the in vitro micro-techniques of cell-mediated cytolysis and inhibition of macrophage migration. T-dependence of MIF production was shown in this system by lymphocyte separation onto T- and B-cells and by inactivation of MIF producers with anti-θ serum. At least part of MIF producers appeared to be more sensitive than killers to the action of anti-θ antibodies in the presence of complement. Production of MIF as compared to the cytotoxic activity was revealed in regional lymph node cells earlier and preserved longer after immunization with allogeneic tumour cells. Immune lymph node cells were shown to produce MIF when incubated with spleen cells of congenic and recombinant strains of mice possessing either private or public H-2 specificities of the immunizing complex, but they did not produce MIF when incubated with syngeneic spleen cells. Removal of killers by absorption on the relevant target cells did not reduce the ability of non-adherent lymphocytes to produce MIF. Unlike cytotoxic activity, MIF production is inhibited by pre-treatment of immune lymphocytes with pronase. The data obtained are indicative of essential differences in effector T-cell subpopulations which exert the cytotoxic effect and produce MIF in the H-2 system. The implications of these data for studies on T-cell differentiation under the action of H-2 antigens are discussed. [ABSTRACT FROM AUTHOR]