Clonal restriction and predominance of regulatory T cells in coronary thrombi of patients with acute coronary syndromes.

AIMS: Regulatory T cells (Treg) exert anti-inflammatory and atheroprotective effects in experimental atherosclerosis. Treg can be induced against specific antigens using immunization strategies associated with clonal restriction. No data exist on Treg in combination with clonal restriction of T cells in patients with acute coronary syndromes (ACS). METHODS AND RESULTS: Among T cell subsets characterized by flow cytometry, Treg (CD4(+) CD25(+) CD127(low)) were twice as frequent in coronary thrombi compared with peripheral blood. Treg prevailed among T cell subsets identified in coronary thrombi. To evaluate clonal restriction, genomic DNA was extracted from coronary thrombi and peripheral blood in order to evaluate T cell receptor (TCR) ß chain diversity by means of Multi-N-plex PCR using a primer specific for all TCR ß V gene segments and another primer specific for TCR ß J gene segments. T cell receptor diversity was reduced in thrombi compared with peripheral blood (intra-individual comparisons in 16 patients) with 8 gene rearrangements in the TCR common in at least 6 out of 16 analysed coronary thrombi. Compared with age-matched healthy controls (n = 16), TCR diversity was also reduced in peripheral blood of patients with ACS; these findings were independent of peripheral T cell numbers. CONCLUSION: We provide novel evidence for a perturbed T cell compartment characterized by clonal restriction in peripheral blood and coronary thrombi from patients with ACS. Our findings warrant further studies on Treg as novel therapeutic targets aimed at enhancing this anti-inflammatory component of adaptive immunity in human atherothrombosis.

Decreased T-cell repertoire diversity in sepsis: a preliminary study.

OBJECTIVE: Septic syndromes are the leading causes of mortality in intensive care units. In patients, the occurrence of sepsis-induced immune suppression is associated with delayed mortality, although the exact role of lymphocyte dysfunctions is not well established. The objective of this study was to investigate T-cell receptor diversity, an important feature of T-cell response, in patients with septic shock. DESIGN: Preliminary prospective observational study. SETTING: Adult intensive care units in a university hospital. SUBJECTS: Patients with septic shock (n = 41) sampled twice after the onset of shock (early after inclusion [day 1] and at the end of the first week [day 7]). MEASUREMENTS AND MAIN RESULTS: Using a novel molecular biology technique, the combinatorial diversity of human T-cell receptor ß-chain (TRB locus) was measured in peripheral blood. Patients with septic shock presented with a marked decreased T-cell receptor diversity after the onset of shock in comparison with normal values. Importantly, in paired samples, a very steep recovery slope of T-cell receptor diversity, never described in other clinical situations, was observed between day 1 and day 7 (p < 0.0001, Wilcoxon's paired test). Decreased T-cell receptor diversity was associated with mortality (log-rank test, p = 0.0058; hazard ratio = 4.48; 95% confidence interval 1.96-53.32), and the development of nosocomial infections (p < 0.05, Mann-Whitney U test). CONCLUSION: Our results show for the first time that septic patients present with a marked decreased T-cell receptor diversity that returned rapidly toward normal values over time. This opens novel cognitive research perspectives that deserve to be investigated in experimental models of sepsis. After confirmation in larger cohorts of these preliminary results, T-cell receptor diversity measurements may become a crucial tool to monitor immune functions in ICU patients.

Lymphopenia combined with low TCR diversity (divpenia) predicts poor overall survival in metastatic breast cancer patients.

Lymphopenia (< 1Giga/L) detected before initiation of chemotherapy is a predictive factor for death in metastatic solid tumors. Combinatorial T cell repertoire (TCR) diversity was investigated and tested either alone or in combination with lymphopenia as a prognostic factor at diagnosis for overall survival (OS) in metastatic breast cancer (MBC) patients. The combinatorial TCR diversity was measured by semi quantitative multi-N-plex PCR on blood samples before the initiation of the first line chemotherapy in a development (n = 66) and validation (n = 67) MBC patient cohorts. A prognostic score, combining lymphocyte count and TCR diversity was evaluated. Univariate and multivariate analyses of prognostic factors for OS were performed in both cohorts. Lymphopenia and severe restriction of TCR diversity called "divpenia" (diversity ≤ 33%) were independently associated with shorter OS. Lympho-divpenia combining lymphopenia and severe divpenia accurately identified patients with poor OS in both cohorts (7.6 and 10.6 vs 24.5 and 22.9 mo). In multivariate analysis including other prognostic clinical factors, lympho-divpenia was found to be an independent prognostic factor in the pooled cohort (p = 0.005) along with lack of HER2 and hormonal receptors expression (p = 0.011) and anemia (p = 0.009). Lympho-divpenia is a novel prognostic factor that will be used to improve quality of MBC patients' medical care.

Activation of classical pathway of complement cascade by soluble oligomers of prion.

Mice defective for C1q complement factor show enhanced resistance to peripheral prion inoculation, and previous work demonstrated a direct interaction between C1q and conformationally modified PrP. However, the nature and physiological consequences of this interaction remain uncharacterized. PrP amino acids 141-159 has been identified as a potential C1q binding site; we show, by both surface plasmon resonance (SPR) spectroscopy and ELISA, that C1q and its globular region bind to PrP mutagenized in the region of interest with comparable efficiency to that of wild-type protein. To test PrP's ability to activate complement, soluble oligomers of the PrP constructs were made. Only PrP and mutagenized PrP oligomers activate the classical complement cascade while PrP monomer and the C-terminal domain, both in oligomeric and in monomeric form, failed to induce activation. This suggests that a conformational change in PrP, which occurs both when PrP is bound to an SPR sensor chip and when it undergoes oligomerization, is requisite for PrP/C1q interaction and activation of the complement cascade. We propose that C1q may act as a natural sensor for prions, leading to activation of the classical complement cascade, which could result in local inflammation and subsequent recruitment of the immune cells that prions initially infect.