Molecular identification of T cells that respond in a primary bulk culture to a peptide derived from a platelet glycoprotein implicated in neonatal alloimmune thrombocytopenia.

Neonatal alloimmune thrombocytopenia induced by the human platelet alloantigen 1a (HPA1a) is characterized by generation of alloantibodies by a mother who is homozygous for the HPA1b alloantigen and almost always HLA-DRB3*0101. The disease is viewed as B cell mediated but the linkage with HLA is indicative of a role for T cells. The HPA1a and HPA1b allotypes are defined, respectively, by Leu and Pro at amino acid 33 of the beta-chain of the platelet integrin GPIIbIIIa (alpha(IIb)beta3). Under the assumption that the same polymorphism may control both the B cell epitope and constitute the MHC-bound peptide, we restimulated PBMC from a woman with an affected child with a synthetic peptide from this polymorphic region. Molecular analysis of the responding T cell repertoire identified two T cells which predominated in cultures stimulated with the alloantigen peptide and which were absent in cultures with the autoantigen peptide. In spite of the use of different V families, sequence of the CDR3 region of the T cell receptor (TCR) beta-chain revealed the presence of a shared motif, L-P-S/T. Oligonucleotide probes specific for the CDR3 sequence indicated that these T cells were present in the PBMC at the highest levels immediately after delivery of the affected infant and their frequency dropped at later times.     

Analysis of human T-cell receptor alpha-chain cDNAs isolated from peripheral blood mononuclear cells.

T-cell receptor alpha-chain cDNA were generated from unstimulated peripheral blood mononuclear cells of a DR2,3,52a individual using a modified anchor PCR method. Fifty-six cDNA clones were identified representing 47 distinct T-cell receptor clonotypes and 26 VA loci. This analysis identified a new VA gene family VA30, and a new member of the VA6 gene family.     

Analysis of human T-cell receptor α-chain cDNAs isolated from peripheral blood mononuclear cells

T-cell receptor α-chain cDNA were generated from unstimulated peripheral blood mononuclear cells of a DR2,3,52a individual using a modified anchor PCR method. Fifty-six cDNA clones were identified representing 47 distinct T-cell receptor clonotypes and 26 VA loci. This analysis identified a new VA gene family VA30, and aew member of the VA6 gene family.     

Selective elimination of alloreactive donor T cells attenuates graft-versus-host disease and enhances T-cell reconstitution.

Impaired T-cell immune reconstitution is a major complication after allogeneic bone marrow transplantation (BMT) and is particularly exacerbated in the setting of graft-versus-host disease (GVHD). Conventional approaches to reduce GVHD, such as T-cell depletion or pharmacologic immunosuppression, typically fail to enhance T-cell immunity and often further exacerbate this problem. An alternative strategy to mitigate GVHD severity is the selective elimination of graft-versus-host-reactive donor T cells by using an incorporated thymidine kinase suicide gene. This approach has been shown to effectively reduce GVHD, although the effect of this strategy on T-cell reconstitution is unresolved. We addressed this question in a murine BMT model (C57BL/6 [H-2(b)] --> AKR/J [H-2(k)]) in which donor and recipient differ at major and minor histocompatibility antigens. Lethally irradiated AKR recipients transplanted with T cell-depleted bone marrow plus thymidine kinase-positive T cells followed by post-BMT ganciclovir (GCV) administration had more prompt and complete normalization of the T-cell repertoire than phosphate-buffered saline-treated GVHD control animals. By 60 days after transplantation, mice administered GCV had T-cell repertoires that were virtually indistinguishable from those of mice that underwent transplantation with T cell-depleted bone marrow alone (no GVHD controls) when assayed by T-cell receptor (TCR) spectratyping. In contrast, phosphate-buffered saline-treated animals had persistent skewing in most Vbeta families. T cells obtained from GCV-treated mice also had significantly higher in vitro proliferative responses after posttransplantation inoculation with ovalbumin than GVHD animals, indicating that CD4(+) T-cell responses against a nominal antigen were better preserved in these chimeras. Finally, GCV-treated mice had augmented immune reconstitution in response to exogenous interleukin-7 administration, as evidenced by increased overall spleen cellularity and absolute numbers of T and B cells. This was in contrast to GVHD control animals, which had a blunted response to interleukin-7 administration. These data indicate that GVHD severity can be significantly reduced by selective elimination of alloreactive donor T cells without compromise of T-cell immunity. Moreover, in light of previous studies demonstrating that this strategy can reduce GVHD without loss of alloengraftment and antileukemia reactivity, further examination of this approach in humans seems warranted.     

Newborns Vitamin A in Relation to Sex and Birth Weight

Cord serum vitamin A values were determined in 256 male and 294 female neonates born in Tehran. The mean cord serum vitamin A values (micrograms/dl +/- SD) was 24.04 +/- 6.87 and ranged from 3.16 to 49.71 micrograms/dl. Males had significantly lower mean cord serum vitamin A values than females (P less than 0.001), and the prevalence of low serum vitamin A (below 20 micrograms/dl) was higher in male neonates than female ones (35 and 21 per cent, respectively). Serum retinol values increased gradually with birth weight. The mean serum vitamin A for premature neonates was significantly lower than term neonates. A significant r value for the linear correlation between cord serum retinol and parity was obtained for mothers aged more than 35 years.     

Vitamin A status and endemic goiter

Serum vitamin A levels were determined in two groups of subjects living in an endemic goiter area in Iran. The first group consisted of 242 non-goitrous subjects, and the second, contained 603 subjects with different grades of goiter. Serum vitamin A concentrations were correlated with goiter, sex, and age. Serum retinol values were not statistically different between goitrous and non-goitrous females, but goitrous male subjects especially those under 13 years of age, had lower serum retinol values than non-goitrous male subjects. The prevalence of low vitamin A levels was higher in goitrous boys. In both groups the prevalence of low serum vitamin A decreased with the increase in age. The prevalence of goiter was not statistically different between boys and girls under 18 years, but was more prevalent in women over 18 years, than men in the same age group (P less than 0.001). This difference was in accordance with serum vitamin A status between women and men after the age of 18 (P less than 0.001). Serum vitamin A increased with age up to 18 years, in both sexes and remained unchanged afterwards. The increase was gradual in girls under 18 years but was sharper in boys during puberty years. Although the values for serum vitamin A in each sex covered wide overlapping ranges, but a general superiority of male serum vitamin A levels over the females was observed.