Skin-homing CLA+ T cells and regulatory CD25+ T cells represent major subsets of human peripheral blood memory T cells migrating in response to CCL1/I-309

Functionally distinct T cell subsets exhibit specific chemokine receptor profiles that regulate their tissue localization. Here, we show that human peripheral blood CD4(+) and CD8(+) cutaneous (CLA(+)), but not intestinal memory (integrin beta(7) (+)) nor IL-4-producing T cells, represent major subpopulations of circulating T cells that specifically migrate in response to the chemokine I-309/CCL1 by virtue of CCR8 expression. Expression of CCR8 is markedly up-regulated upon activation and in vitro culture of human CLA(+) T cells, suggesting the involvement of CCR8 in localization of cutaneous memory T cells to the skin. Interestingly, amongst circulating memory CD4(+)CD45RO(+) T cells, chemotactic responsiveness to CCL1 is restricted to cells expressing CD25 and/or CLA surface markers for regulatory T cells (Treg) and skin-homing T cells and maximal responsiveness is observed on CLA(+)CD25(+)T cells. Such pattern of CCL1 responsiveness suggests that the CCR8/CCL1 axis may regulate trafficking of cutaneous Treg and memory T cells into the skin.     

Identification of a Promiscuous T-Cell Epitope in Mycobacterium tuberculosis Mce Proteins

The characterization of Mycobacterium tuberculosis antigens inducing CD4(+) T-cell responses could critically contribute to the development of subunit vaccines for M. tuberculosis. Here we performed computational analysis by using T-cell epitope prediction software (known as TEPITOPE) to predict promiscuous HLA-DR ligands in the products of the mce genes of M. tuberculosis. The analysis of the proliferative responses of CD4(+) T cells from patients with pulmonary tuberculosis to selected peptides displaying promiscuous binding to HLA-DR in vitro led us to the identification of a peptide that induced proliferation of CD4(+) cells from 50% of the tested subjects. This study demonstrates that a systematic computational approach can be used to identify T-cell epitopes in proteins expressed by an intracellular pathogen.     

Plasmodium falciparum-specific human T cell clones: recognition of different parasite antigens

T lymphocyte clones specific for malarial (Plasmodium falciparum) blood stage antigens were obtained from acutely infected patients or from donors living in a malaria-endemic area of West Africa. Thirty-four clones carrying the CD4 antigen, and one CD8+ clone, were tested in a proliferation assay for their capacity to recognize P. falciparum isolates of different geographical origins. Only one clone distinguished between different parasite isolates (it failed to react with a parasite isolate originating from East Africa, but did recognize West African and Asian isolates). All of the clones responded well to intact erythrocytes containing viable parasites, but some responded poorly to extracts of parasitized cells. Eight of 19 clones studied (all CD4+) recognized parasite antigens which had characteristic mobilities in sodium dodecyl sulfate-containing polyacrylamide gels. The antigens had apparent molecular weights of about 20,000, 35,000, 40,000, 120,000, 150,000-200,000 and 200,000. These results (together with a previous report of two clones recognizing an antigen of molecular weight about 50,000, Sinigaglia and Pink, EMBO J. 1985. 4:3819) show that T cells in infected individuals react with at least 6 different parasite proteins.     

Substitution of aspartic acid at beta57 with alanine alters MHC class II peptide binding activity but not protein stability: HLA-DQ (alpha1*0201, beta1*0302) and (alpha1*0201, beta1*0303)

In class II major histocompatibility complex (MHC) proteins, residue beta57 is usually aspartic acid. Alleles carrying serine, valine, or alanine at this position are strongly correlated with the development of insulin-dependent diabetes mellitus (IDDM). Asp(beta)57 participates in a conserved salt bridge that bridges the alpha and beta subunits in the peptide-binding site. It has been proposed that the correlation between IDDM and MHC alleles lacking Asp(beta)57 may be due to an instability of the protein caused by loss of this salt bridge. Using a pair of HLA-DQ proteins (alpha1*0201, beta1*0302) and (alpha1*0201, beta1*0303) differing only in having aspartic acid or alanine at position beta57, we show that the polymorphism does not have a significant effect on protein stability for either the empty or peptide-loaded forms. However, the circular dichroism spectra indicate that empty and peptide-loaded Alabeta57 proteins display slightly different secondary structures relative to their Aspbeta57 counterparts. A set of three peptides shows different binding affinities for DQ(alpha1*0201, beta1*0302) relative to DQ(alpha1*0201, beta1*0303). We propose that substitution of Asp(beta)57 residue causes a local rearrangement within the DQ peptide-binding site that alters the peptide-binding specificity. This rearrangement may help to explain the previously observed differences in SDS stability between Asp and non-Asp(beta)57 DQ proteins.     

Transient osteoporosis of the Hip: a densitometric study

Summary Three new cases of transient osteoporosis of the hip are reported. Diagnosis was achieved by plain radiographs, bone scintiscan, magnetic resonance imaging and X-ray absorptiometry of proximal femurs. The densitometry showed at the Ward's triangle a mean reduction of bone mineral density in the affected side of 36%. All subjects were treated with i.v. clodronate for ten consecutive days with a complete recovery of femoral density within 4 months. X-ray absorptiometry allows a quantification of the demineralization process and can be useful in the long term evaluation of this entity.     

The role of plasma fibronectin in platelet adhesion to collagen

Human washed platelets were eluted from columns of Sepharose 4B linked to different preparations of collagen in order to evaluate cell adhesion. Collagen preparations characterized by low and high affinity toward platelets were identified. In our experiments, fibronectin purified from human plasma modified platelet adhesiveness, though not dramatically. When washed platelets, resuspended in a buffer containing fibronectin, were filtered on a low-affinity collagen-Sepharose, a significant increase in their adhesion occurred. A similar modification could be observed when platelets were allowed to adhere to the same collagen-Sepharose preconditioned with fibronectin. The effect of fibronectin was otherwise negligible when the high-affinity collagen was used for the experiments.     

Ageing of rabbit red cells in vitro: membrane modifications and their possible role in red cell survival in vivo

In vitro incubation induces, in rabbit red cell membranes, significant modifications consisting mainly in a decrease of sialic acid and galactose. In vivo the life span of incubated erythrocytes seems to be correlated to the degree of surface alterations and ATP depletion: larger surface modifications and energy charge reduction induce shorter survival time. It can therefore be postulated that incubation of red cell in vitro can cause an ageing process similar to that occurring physiologically in vivo.     

Severe platelet dysfunction in a patient with autoantibodies against membrane glycoproteins IIb-IIIa

A young women affected by Hodgkin's disease developed chronic autoimmune thrombocytopenic purpura. Splenectomy induced normalization of her platelet count, but hemorrhagic symptoms did not disappear. The patient's platelets did not aggregate in response to collagen and ADP and the IgG fraction of the patient's plasma induced the same defect in normal platelets. The women's IgG recognized glycoproteins IIb and IIIa of normal platelet membranes. Prednisone therapy induced the disappearance of bleeding symptoms and the normalization of platelet aggregation.