Diversity of T-cell receptor V alpha, V beta, and CDR3 expression by myelin basic protein-specific human T-cell clones.

We sequenced the cDNAs of alpha and beta T-cell receptors (TCRs), including V, J, and CDR3 regions, expressed by 54 myelin basic protein (MBP)-specific T-cell clones generated from the peripheral blood of 15 multiple sclerosis (MS) patients and three normal controls. Thirteen V alpha gene segments, 18 V beta gene segments, 23 CDR3 alpha sequences, and 30 CDR3 beta sequences were represented among these clones. Some CDR3 motifs were common to several clones that shared epitope specificity, while other motifs were common to clones with diverse epitope specificities. The extensive heterogeneity of TCR gene expression in the human immune response to MBP indicates that therapeutic strategies aimed at blocking a limited number of TCRs are unlikely to fully suppress the T-cell response to MBP in vivo.

Alloantigen presenting function of normal human CD34+ hematopoietic cells.

The identification of the CD34 molecule, expressed almost exclusively on human hematopoietic stem cells and committed progenitors, and the development of CD34-specific monoclonal antibodies have made procurement of relatively pure populations of CD34+ marrow cells for autologous transplantation feasible. Characterization of the immunogenicity of CD34+ marrow cells may facilitate the design of successful strategies to use these cells for allogeneic transplantation. CD34+ marrow cells from normal volunteers were enriched to greater than 98% purity by immunoaffinity chromatography on column followed by fluorescence-activated cell sorting. Purified CD34+ cells were tested for expression of HLA-DR and other accessory molecules, and function in hematopoietic colony growth and mixed leukocyte culture (MLC) assays. Greater than 95% CD34+ cells were positive for HLA-DR and 74% +/- 10% were highly positive for CD18, the common beta-chain of a leukointegrin family. CD34+/CD18- cells were small, agranular lymphocytes which contained the majority of precursors for colony-forming cells detected in long-term cultures. They produced almost no stimulation of purified T cells from HLA-DR-incompatible individuals in bulk MLC or in limiting dilution assay. In contrast, CD34+/CD18+ cells were large, were enriched for cells forming mixed colonies in short- but not long-term assays, and were capable of stimulating allogeneic T cells. CD86, a natural ligand for the T-cell activation molecule CD28, was coexpressed with CD18 in 6% +/- 3% of CD34+ cells. CD34+/CD86+ cells, but not CD34+/CD86- cells, exhibited strong alloantigen presenting function. Thus, pluripotent hematopoietic activity and alloantigen presenting function are attributes of distinct subsets of CD34+ marrow cells. CD34+/CD18- or CD34+/CD86- cells may be more effective than either the whole CD34+ population or unseparated marrow in engrafting allogeneic recipients and may also facilitate induction of tolerance.

Deficient expression in multiple sclerosis of the inhibitory transcription factor Sp3 in mononuclear blood cells.

To evaluate differential gene expression in multiple sclerosis (MS) patients and control subjects, we used differential display to screen for messenger RNAs that are differentially expressed in peripheral blood mononuclear cells from monozygotic twins who are discordant for MS. We identified a 232-bp complementary DNA fragment, present only in material from the normal twin, that exhibited 100% identity with the inhibitory transcription factor Sp3. Oligonucleotide primers corresponding to Sp3 messenger RNA sequences amplified complementary DNA of appropriate size from 83% of control subjects but from only 21% of MS patients (p < 0.001). These results suggest that Sp3 gene transcription is suppressed in peripheral blood mononuclear cells from most MS patients and that other genes whose expression is normally suppressed by Sp3 in immune cells may consequently be overexpressed.