Discrimination of T-cell subsets and T-cell receptor repertoire distribution

HIV rapidly targets a diverse pool of CD4+ T cells to establish productive and latent infections

Upon infection, HIV disseminates throughout the human body within 1-2 weeks. However, its early cellular targets remain poorly characterized. We used a single-cell approach to retrieve the phenotype and TCR sequence of infected cells in blood and lymphoid tissue from individuals at the earliest stages of HIV infection. HIV initially targeted a few proliferating memory CD4+ T cells displaying high surface expression of CCR5. The phenotype of productively infected cells differed by Fiebig stage and between blood and lymph nodes. The TCR repertoire of productively infected cells was heavily biased, with preferential infection of previously expanded and disseminated clones, but composed almost exclusively of unique clonotypes, indicating that they were the product of independent infection events. Latent genetically intact proviruses were already archived early in infection. Hence, productive infection is initially established in a pool of phenotypically and clonotypically distinct T cells, and latently infected cells are generated simultaneously.

A Critical Review on the Standardization and Quality Assessment of Nonfunctional Laboratory Tests Frequently Used to Identify Inborn Errors of Immunity

Inborn errors of immunity (IEI), which were previously termed primary immunodeficiency diseases, represent a large and growing heterogeneous group of diseases that are mostly monogenic. In addition to increased susceptibility to infections, other clinical phenotypes have recently been associated with IEI, such as autoimmune disorders, severe allergies, autoinflammatory disorders, benign lymphoproliferative diseases, and malignant manifestations. The IUIS 2019 classification comprises 430 distinct defects that, although rare individually, represent a group affecting a significant number of patients, with an overall prevalence of 1:1,200-2,000 in the general population. Early IEI diagnosis is critical for appropriate therapy and genetic counseling, however, this process is deeply dependent on accurate laboratory tests. Despite the striking importance of laboratory data for clinical immunologists, several IEI-relevant immunoassays still lack standardization, including standardized protocols, reference materials, and external quality assessment programs. Moreover, well-established reference values mostly remain to be determined, especially for early ages, when the most severe conditions manifest and diagnosis is critical for patient survival. In this article, we intend to approach the issue of standardization and quality control of the nonfunctional diagnostic tests used for IEI, focusing on those frequently utilized in clinical practice. Herein, we will focus on discussing the issues of nonfunctional immunoassays (flow cytometry, enzyme-linked immunosorbent assays, and turbidimetry/nephelometry, among others), as defined by the pure quantification of proteins or cell subsets without cell activation or cell culture-based methods.

The Value of Flow Cytometry Clonality in Large Granular Lymphocyte Leukemia

Simple Summary

Large granular lymphocyte (LGL) leukemia, a lymphoproliferative disease, is characterized by an increased frequency of large-sized lymphocytes with typical expression of T-cell receptor (TCR) αβ, CD3, CD8, CD16, CD45RA, and CD57, and with the expansion of one to three subfamilies of the TCR variable β chain reflecting gene rearrangements. Molecular analysis remains the gold standard for confirmation of TCR clonality; however, flow cytometry is time and labor saving, and can be associated with simultaneous investigation of other surface markers. Moreover, Vβ usage by flow cytometry can be employed for monitoring clonal kinetics during treatment and follow-up of LGL leukemia patients.

Abstract

Large granular lymphocyte (LGL) leukemia is a lymphoproliferative disorder of mature T or NK cells frequently associated with autoimmune disorders and other hematological conditions, such as myelodysplastic syndromes. Immunophenotype of LGL cells is similar to that of effector memory CD8⁺ T cells with T-cell receptor (TCR) clonality defined by molecular and/or flow cytometric analysis. Vβ usage by flow cytometry can identify clonal TCR rearrangements at the protein level, and is fast, sensitive, and almost always available in every Hematology Center. Moreover, Vβ usage can be associated with immunophenotypic characterization of LGL clone in a multiparametric staining, and clonal kinetics can be easily monitored during treatment and follow-up. Finally, Vβ usage by flow cytometry might identify LGL clones silently underlying other hematological conditions, and routine characterization of Vβ skewing might identify recurrent TCR rearrangements that might trigger aberrant immune responses during hematological or autoimmune conditions.

Deep sequencing and flow cytometric characterization of expanded effector memory CD8+CD57+ T cells frequently reveals T-cell receptor Vβ oligoclonality and CDR3 homology in acquired aplastic anemia

Oligoclonal expansion of CD8⁺ CD28⁻ lymphocytes has been considered indirect evidence for a pathogenic immune response in acquired aplastic anemia. A subset of CD8⁺ CD28⁻ cells with CD57 expression, termed effector memory cells, is expanded in several immune-mediated diseases and may have a role in immune surveillance. We hypothesized that effector memory CD8⁺CD28⁻CD57⁺ cells may drive aberrant oligoclonal expansion in aplastic anemia. We found CD8⁺CD57⁺ cells frequently expanded in the blood of aplastic anemia patients, with oligoclonal characteristics by flow cytometric Vβ usage analysis: skewing in 1–5 Vβ families and frequencies of immunodominant clones ranging from 1.98% to 66.5%. Oligoclonal characteristics were also observed in total CD8⁺ cells from aplastic anemia patients with CD8⁺CD57⁺ cell expansion by T-cell receptor deep sequencing, as well as the presence of 1–3 immunodominant clones. Oligoclonality was confirmed by T-cell receptor repertoire deep sequencing of enriched CD8⁺CD57⁺ cells, which also showed decreased diversity compared to total CD4⁺ and CD8⁺ cell pools. From analysis of complementarity-determining region 3 sequences in the CD8⁺ cell pool, a total of 29 sequences were shared between patients and controls, but these sequences were highly expressed in aplastic anemia subjects and also present in their immunodominant clones. In summary, expansion of effector memory CD8⁺ T cells is frequent in aplastic anemia and mirrors Vβ oligoclonal expansion. Flow cytometric Vβ usage analysis combined with deep sequencing technologies allows high resolution characterization of the T-cell receptor repertoire, and might represent a useful tool in the diagnosis and periodic evaluation of aplastic anemia patients. (Registered at clinicaltrials.gov identifiers: 00001620, 01623167, 00001397, 00071045, 00081523, 00961064)

Age and gender leucocytes variances and references values generated using the standardized ONE-Study protocol

Flow cytometry is now accepted as an ideal technology to reveal changes in immune cell composition and function. However, it is also an error-prone and variable technology, which makes it difficult to reproduce findings across laboratories. We have recently developed a strategy to standardize whole blood flow cytometry. The performance of our protocols was challenged here by profiling samples from healthy volunteers to reveal age- and gender-dependent differences and to establish a standardized reference cohort for use in clinical trials. Whole blood samples from two different cohorts were analyzed (first cohort: n = 52, second cohort: n = 46, both 20-84 years with equal gender distribution). The second cohort was run as a validation cohort by a different operator. The "ONE Study" panels were applied to analyze expression of >30 different surface markers to enumerate proportional and absolute numbers of >50 leucocyte subsets. Indeed, analysis of the first cohort revealed significant age-dependent changes in subsets e.g. increased activated and differentiated CD4(+) and CD8(+) T cell subsets, acquisition of a memory phenotype for Tregs as well as decreased MDC2 and Marginal Zone B cells. Males and females showed different dynamics in age-dependent T cell activation and differentiation, indicating faster immunosenescence in males. Importantly, although both cohorts consisted of a small sample size, our standardized approach enabled validation of age-dependent changes with the second cohort. Thus, we have proven the utility of our strategy and generated reproducible reference ranges accounting for age- and gender-dependent differences, which are crucial for a better patient monitoring and individualized therapy. © 2016 International Society for Advancement of Cytometry.

T-cell receptor Vβ repertoire of CD8+ T-lymphocyte subpopulations in cutaneous leishmaniasis patients from the state of Rio de Janeiro, Brazil

In human cutaneous leishmaniasis (CL), the immune response is mainly mediated by T-cells. The role of CD8⁺ T-lymphocytes, which are related to healing or deleterious functions, in affecting clinical outcome is controversial. The aim of this study was to evaluate T-cell receptor diversity in late-differentiated effector (LDE) and memory CD8⁺ T-cell subsets in order to create a profile of specific clones engaged in deleterious or protective CL immune responses. Healthy subjects, patients with active disease (PAD) and clinically cured patients were enrolled in the study. Total CD8⁺ T-lymphocytes showed a disturbance in the expression of the Vβ2, Vβ9, Vβ13.2, Vβ18 and Vβ23 families. The analyses of CD8⁺T-lymphocyte subsets showed high frequencies of LDE CD8⁺T-lymphocytes expressing Vβ12 and Vβ22 in PAD, as well as effector-memory CD8⁺ T-cells expressing Vβ22. We also observed low frequencies of effector and central-memory CD8⁺ T-cells expressing Vβ2 in PAD, which correlated with a greater lesion size. Particular Vβ expansions point to CD8⁺ T-cell clones that are selected during CL immune responses, suggesting that CD8⁺ T-lymphocytes expressing Vβ12 or Vβ22 are involved in a LDE response and that Vβ2 contractions in memory CD8⁺T-cells are associated with larger lesions.

Apoptosis and frequency of total and effector CD8+ T lymphocytes from cutaneous leishmaniasis patients during antimonial therapy

BACKGROUND

Leishmaniasis is an important parasitic disease affecting millions worldwide. Human cutaneous leishmaniasis (CL) is endemic in Rio de Janeiro, Brazil, where is caused by Leishmania braziliensis. The adaptive immune response is accountable for the healing of CL and despite of key role of CD8+ T cells in this immune response little is known about the CD8+ T lymphocytes frequencies, apoptosis and antigen-responsive CD8+ T lymphocytes of CL patients during antimonial therapy.

METHODS

Using flow cytometry, we examined total and effector CD8+ T cells from CL patients before (PBT), during (PDT) and after (PAT) treatment for apoptosis and frequencies upon isolation and after in vitro L. braziliensis antigens (LbAg)-stimulation culture. Besides, a correlation study between immunological findings and lesion size was done.

RESULTS

PDT showed lower frequencies of total CD8+ T lymphocytes and higher levels of apoptosis of these cells, which were also observed following LbAg-stimulation culture. Regarding effector CD8+ T cells, high frequencies were observed in PDT, while lower frequencies were observed in PAT. Interestingly, PDT showed higher frequencies of apoptotic-effector CD8+ T lymphocytes. Similar results were seen after in vitro antigenic-stimulation assays. Correlation analysis showed that the greater the size of lesion, the smaller the frequency of effector CD8+ T lymphocytes in PDT and PAT, as well as a positive correlation between apoptotic-effector CD8+ T cells frequency and lesion size of PDT.

CONCLUSIONS

Changes in effector CD8+ T-lymphocyte frequencies, during and after treatment, seem to represent a critical stage to generate an efficient immune response and suggest that these cells would be evolved in the triggering or in the resolution of lesion, under the influence of therapy. This hypothesis opens new perspectives to clarify controversial statements about the protective or deleterious role of CD8+ T cells in the cure or aggravation of CL and the new approach of evaluating patients during treatment proved to be of utmost importance for understanding the immune response in the healing process of human CL.

Semi-automated and standardized cytometric procedures for multi-panel and multi-parametric whole blood immunophenotyping

Immunophenotyping by multi-parametric flow cytometry is the cornerstone technology for enumeration and characterization of immune cell populations in health and disease. Standardized procedures are essential to allow for inter-individual comparisons in the context of population based or clinical studies. Herein we report the approach taken by the Milieu Intérieur Consortium, highlighting the standardized and automated procedures used for immunophenotyping of human whole blood samples. We optimized eight-color antibody panels and procedures for staining and lysis of whole blood samples, and implemented pre-analytic steps with a semi-automated workflow using a robotic system. We report on four panels that were designed to enumerate and phenotype major immune cell populations (PMN, T, B, NK cells, monocytes and DC). This work establishes a foundation for defining reference values in healthy donors. Our approach provides robust protocols for affordable, semi-automated eight-color cytometric immunophenotyping that can be used in population-based studies and clinical trial settings.

Complement protein C1q bound to apoptotic cells suppresses human macrophage and dendritic cell-mediated Th17 and Th1 T cell subset proliferation

A complete genetic deficiency of the complement protein C1q results in SLE with nearly 100% penetrance in humans, but the molecular mechanisms responsible for this association have not yet been fully determined. C1q opsonizes ACs for enhanced ingestion by phagocytes, such as Mϕ and iDCs, avoiding the extracellular release of inflammatory DAMPs upon loss of the membrane integrity of the dying cell. We previously showed that human monocyte-derived Mϕ and DCs ingesting autologous, C1q-bound LALs (C1q-polarized Mϕ and C1q-polarized DCs), enhance the production of anti-inflammatory cytokines, and reduce proinflammatory cytokines relative to Mϕ or DC ingesting LAL alone. Here, we show that C1q-polarized Mϕ have elevated PD-L1 and PD-L2 and suppressed surface CD40, and C1q-polarized DCs have higher surface PD-L2 and less CD86 relative to Mϕ or DC ingesting LAL alone, respectively. In an MLR, C1q-polarized Mϕ reduced allogeneic and autologous Th17 and Th1 subset proliferation and demonstrated a trend toward increased Treg proliferation relative to Mϕ ingesting LAL alone. Moreover, relative to DC ingesting AC in the absence of C1q, C1q-polarized DCs decreased autologous Th17 and Th1 proliferation. These data demonstrate that a functional consequence of C1q-polarized Mϕ and DC is the regulation of Teff activation, thereby "sculpting" the adaptive immune system to avoid autoimmunity, while clearing dying cells. It is noteworthy that these studies identify novel target pathways for therapeutic intervention in SLE and other autoimmune diseases.