Possible different mechanisms of B cell activation in systemic lupus erythematosus and rheumatoid arthritis: opposite expression of low-affinity receptors for IgE (CD23) on their peripheral B cells

To clarify the differential state of B cell activation in patients with systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA), we investigated the expression of low-affinity receptor for IgE (Fc epsilon RII; CD23) on their peripheral B cells by a cytofluorometry using H107 (CD23) and Leu-16 (CD20) monoclonal antibodies. The percentage of CD23-negative B cells in total lymphocytes was significantly greater in both groups of patients than in normal subjects, suggesting the hyperactivity of late-phase B cells in both diseases. However, the increase of CD23-negative B cells in RA was brought about by the increased number of total B cells, although that in SLE was mainly based on the relative decrease of CD23-positive B cells. The number of IgD-positive B cells was decreased, and the number of colony-forming B cells was markedly increased in SLE patients. These observations indicate that a B cell abnormality is mainly qualitative in SLE but quantitative in RA.

Limited proteolysis of bovine myelin basic protein by calcium-dependent proteinase from bovine spinal cord

In order to shed some light on the role of proteinases in the process of demyelination in the central nervous system, a calcium-dependent proteinase was purified to homogeneity from bovine spinal cord, and its action on myelin basic protein purified from the same tissue was investigated. Among the three major myelin basic protein fractions, Fraction I was resistant to the action of the enzyme whereas Fractions II and III were degraded in the same manner, giving two major bands on SDS-polyacrylamide gel electrophoresis. The hydrolysis products were fractionated by high-performance liquid chromatography and characterized. The results showed that the myelin basic protein (Fractions II and III) was rather selectively cleaved at the Val93-Thr94 bond and the Arg96-Thr97 bond in mutually exclusive ways, with minor cleavages at the Ala16-Ser17 and Gly68-Ser69 bonds, suggesting the implication in vivo of calcium-dependent proteinase in the limited proteolysis of myelin basic protein.

Differentiation of an interleukin 3-dependent precursor B-cell clone into immunoglobulin-producing cells in vitro

Precursors to B-cell lines with immunoglobulin genes in the germ-line context have been shown to be capable of generating mature B cells in vivo. We report here that an interleukin 3-dependent precursor B-cell line, LyD9, differentiated in vitro into mature B cells, producing IgM and IgG by coculture with bone marrow accessory (or stroma) cells or with dendritic cells and T cells. Up to 50% of IgM-positive cells, but no Thy-1-positive cells, appeared after the 7- to 10-day coculture. Induced LyD9 cells underwent heterogenous immunoglobulin gene rearrangement and synthesized mRNAs encoding immunoglobulin mu, gamma, and kappa chains. However, these cells did not show any rearrangement of genes encoding the alpha and beta chains of the T-cell receptor. The induction of differentiation by coculture with bone marrow stroma cells was blocked by anti-lymphocyte function-associated antigen 1 or anti-interleukin 4 antibody. These systems are useful for molecular biological studies on regulation of differentiation of bone marrow-derived cells into the B-cell lineage.

B cell repertoire for anti-DNA antibody in normal and lupus mice: differential expression of precursor cells for high and low affinity anti-DNA antibodies

The precursor frequency for anti-DNA antibody producing cells and the affinity of antibodies secreted by these cells in both immature prereceptor B cell populations and mature B cell populations were compared between 8-week-old C57BL/6 female mice and 9-month-old B/WF1 female mice by producing a large collection of IgM secreting hybridomas from LPS-stimulated B cells. The data indicate that precursor cells for high affinity anti-DNA antibody are eliminated as they mature in C57BL/6 mice, while a sizable number of such clones are present in mature splenic B cells of aged B/WF1 mice. These results suggest that the emergence of precursors for high affinity anti-DNA producing cells in mature B cell population is an important factor in the pathogenesis of SLE.

Limiting dilution analysis of the stem cells for T cell lineage

Stem cell activities of bone marrow, spleen, thymus, and fetal liver cells for T cell lineage were studied comparatively by transferring the cells from these organs through i.v. or intrathymus (i.t.) route into right leg- and tail-shielded (L-T-shielded) and 900 R-irradiated recipient mice, which were able to survive without supplying hemopoietic stem cells. Cells from B10.Thy-1.1 (H-2b, Thy-1.1) mice were serially diluted and were transferred into L-T-shielded and irradiated C57BL/6 (H-2b, Thy-1.2) mice, and 21 days later the thymus cells of recipient mice were assayed for Thy-1.1+ cells by flow cytofluorometry. The percentage of recipient mice possessing donor-type T cells was plotted against the number of cells transferred, and the stem cell activity in each cell source was expressed as the 50% positive value, the number of donor cells required for generating donor-type T cells in the thymuses of 50% of recipient mice. In i.v. transfer experiments, the activity of bone marrow cells was similar to that of fetal liver cells, and about 100 times and nearly 1000 times higher than those of spleen cells and thymus cells, respectively. In i.t. transfer experiments, the number of cells required for generating donor-type T cells was much lower than that in i.v. transfer experiments, although the ratio in 50% positive values between i.v. and i.t. transfers differed among cell sources. In i.t. transfers, the 50% positive value of bone marrow cells was five times, 400 times, and 500 times higher than that of fetal liver cells, spleen cells, and thymus cells, respectively. Our previous finding that stem cells are enriched in the spleens of mice which were whole body-irradiated and marrow-reconstituted 7 days earlier was confirmed also by the present limiting dilution assay carried out in i.v. as well as i.t. transfers.

Limiting dilution analysis of the stem cells for T cell lineage

Stem cell activities of bone marrow, spleen, thymus, and fetal liver cells for T cell lineage were studied comparatively by transferring the cells from these organs through i.v. or intrathymus (i.t.) route into right leg- and tail-shielded (L-T-shielded) and 900 R-irradiated recipient mice, which were able to survive without supplying hemopoietic stem cells. Cells from B10.Thy-1.1 (H-2b, Thy-1.1) mice were serially diluted and were transferred into L-T-shielded and irradiated C57BL/6 (H-2b, Thy-1.2) mice, and 21 days later the thymus cells of recipient mice were assayed for Thy-1.1+ cells by flow cytofluorometry. The percentage of recipient mice possessing donor-type T cells was plotted against the number of cells transferred, and the stem cell activity in each cell source was expressed as the 50% positive value, the number of donor cells required for generating donor-type T cells in the thymuses of 50% of recipient mice. In i.v. transfer experiments, the activity of bone marrow cells was similar to that of fetal liver cells, and about 100 times and nearly 1000 times higher than those of spleen cells and thymus cells, respectively. In i.t. transfer experiments, the number of cells required for generating donor-type T cells was much lower than that in i.v. transfer experiments, although the ratio in 50% positive values between i.v. and i.t. transfers differed among cell sources. In i.t. transfers, the 50% positive value of bone marrow cells was five times, 400 times, and 500 times higher than that of fetal liver cells, spleen cells, and thymus cells, respectively. Our previous finding that stem cells are enriched in the spleens of mice which were whole body-irradiated and marrow-reconstituted 7 days earlier was confirmed also by the present limiting dilution assay carried out in i.v. as well as i.t. transfers.

Tac antigen-positive T cells activated in autologous mixed lymphocyte reaction regulate the generation of killer T cells against hapten-modified autologous cells

T cells that proliferate in the autologous mixed lymphocyte reaction (auto-MLR) have been shown to acquire some suppressor or regulatory activities. In the present study, we examined the suppressive effects of T cells activated in the auto-MLR on the induction of hapten-specific cytotoxic T cells. NRFT (depletion of ARFT from UT) were used as the responder cells of TNP-MLR. After primary and secondary TNP-MLR, the cells were harvested and tested for their cytotoxic activities against TNP-modified autologous cells by 51Cr-release assay. When UT cells cultured for 1 wk in auto-MLR were added to primary TNP-MLR at the beginning of culture, the cytotoxic activity tested at the end of the culture was suppressed from 15.6% +/- 2.7 to 5.8% +/- 1.1 (percent cytotoxicity, mean +/- SE). However, these auto-MLR-activated UT cells had little suppressive activity against cytotoxic T cells when they were added to the final assay of TNP-CTR. Suppressive activities of these cells on the generation of cytotoxic T cells during secondary TNP-MLR were also tested. The addition of auto-MLR-activated UT cells to the secondary TNP-MLR at the beginning of the culture reduced the cytotoxic activities of NRFT from 23.8% +/- 2.3 to 9.7% +/- 1.7 after secondary TNP-MLR. Allo-activated T cells, PHA blasts, and fresh autologous T cells were used as the controls, but none of the cells had suppressive effects on the generation of CTL. Characteristics of these suppressor cells were examined. Auto-MLR-activated cells from ARFT fractions exhibit very powerful suppressor activity. Treatment of the auto-MLR-activated T cells with mitomycin C eliminated their suppressive effects on the generation of CTL; 21.2% +/- 6.3 of UT cells became anti-Tac positive after 1 wk of auto-MLR. Treatment of auto-MLR-activated UT cells with anti-Tac antibody plus complement eliminated their suppressive activities on the induction of CTL. Thus, T cells stimulated in auto-MLR were shown to have suppressive effects on the induction of cytotoxic T cells against TNP-modified autologous cells. These cells were mitomycin C sensitive. Because anti-Tac antibody is reactive to activated T cells, activation of T cells during auto-MLR was thought to be necessary for the acquisition of the suppressive activity.

Tac antigen-positive T cells activated in autologous mixed lymphocyte reaction regulate the generation of killer T cells against hapten-modified autologous cells

T cells that proliferate in the autologous mixed lymphocyte reaction (auto-MLR) have been shown to acquire some suppressor or regulatory activities. In the present study, we examined the suppressive effects of T cells activated in the auto-MLR on the induction of hapten-specific cytotoxic T cells. NRFT (depletion of ARFT from UT) were used as the responder cells of TNP-MLR. After primary and secondary TNP-MLR, the cells were harvested and tested for their cytotoxic activities against TNP-modified autologous cells by 51Cr-release assay. When UT cells cultured for 1 wk in auto-MLR were added to primary TNP-MLR at the beginning of culture, the cytotoxic activity tested at the end of the culture was suppressed from 15.6% +/- 2.7 to 5.8% +/- 1.1 (percent cytotoxicity, mean +/- SE). However, these auto-MLR-activated UT cells had little suppressive activity against cytotoxic T cells when they were added to the final assay of TNP-CTR. Suppressive activities of these cells on the generation of cytotoxic T cells during secondary TNP-MLR were also tested. The addition of auto-MLR-activated UT cells to the secondary TNP-MLR at the beginning of the culture reduced the cytotoxic activities of NRFT from 23.8% +/- 2.3 to 9.7% +/- 1.7 after secondary TNP-MLR. Allo-activated T cells, PHA blasts, and fresh autologous T cells were used as the controls, but none of the cells had suppressive effects on the generation of CTL. Characteristics of these suppressor cells were examined. Auto-MLR-activated cells from ARFT fractions exhibit very powerful suppressor activity. Treatment of the auto-MLR-activated T cells with mitomycin C eliminated their suppressive effects on the generation of CTL; 21.2% +/- 6.3 of UT cells became anti-Tac positive after 1 wk of auto-MLR. Treatment of auto-MLR-activated UT cells with anti-Tac antibody plus complement eliminated their suppressive activities on the induction of CTL. Thus, T cells stimulated in auto-MLR were shown to have suppressive effects on the induction of cytotoxic T cells against TNP-modified autologous cells. These cells were mitomycin C sensitive. Because anti-Tac antibody is reactive to activated T cells, activation of T cells during auto-MLR was thought to be necessary for the acquisition of the suppressive activity.