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Alymphoplasia (aly) mice are thought to provide a new model for systemic Sjögren's syndrome (SS), since they reveal remarkable infiltration of mononuclear cells into salivary glands, lachrymal glands and kidneys, and show histological findings similar to those in patients with SS. Cell transfer experiments demonstrate that T cells induce the infiltration of mononuclear cells into several tissues in aly mice. To analyse the pathogenesis of cell infiltration in various tissues, we examined T-cell receptor (TCR) V beta usage of T cells in salivary glands, lachrymal glands and kidneys from aly mice, using family-polymerase chain reaction (PCR) and PCR-single-strand conformation polymorphism (SSCP) methods. The results of SSCP demonstrated that the infiltrating T cells in the three organs expanded clonally, suggesting that they proliferate by antigen-driven stimulation. Some TCR V beta genes (V beta 1, 3, 6, 11, 12, 16) were commonly used in salivary glands, lachrymal glands and kidneys, while the V beta 7 gene was specifically expressed in kidneys. SSCP also showed that there were a few shared T-cell clones (V beta 3- and V beta 6-positive cells) among the three tissues. Indeed, sequence analysis of accumulated T cells showed that a conserved amino acid (leucine) at position 98 in the TCR V beta complementary determining region (CDR) 3 was detected in all organs at high frequency (41-57%) and the amino acid sequence motif (LG) was specifically conserved at a frequency of 32% in the three organs. In conclusion, T cells that infiltrate into lachrymal glands, salivary glands and kidneys of aly mutant mice might recognize shared common epitopes in all three organs and a kidney-specific antigen.

The precursor frequency for anti-DNA antibody-producing cells in the pre-immune B cell repertoire was investigated in young female BALB/c and NZW mice, and in young and aged female NZB x NZWF1 (B/WF1) mice. Spleen cells from these mice were diluted serially and stimulated polyclonally in vitro with lipopolysaccharide (LPS) and IL-4 to induce both IgM and IgG1 production. The results demonstrated that there existed virtually no difference in precursor frequency for IgM anti-DNA antibody-producing cells between normal and lupus mice, confirming previous observations made by other investigators. In contrast, the number of precursors for IgG1 anti-DNA antibody-producing cells was much higher in young and old B/WF1 mice than in normal mice. These results suggest that the high frequency of precursors for IgG1 anti-DNA antibody-producing cells in the pre-immune B cell repertoire of B/WF1 mice is a crucial factor for the pathogenesis of systemic lupus erythematosus.

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.

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.

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.