The Enigmatic Nature of the TCR-pMHC Interaction: Implications for CAR-T and TCR-T Engineering

The interaction of the T-cell receptor (TCR) with a peptide in the major histocompatibility complex (pMHC) plays a central role in the adaptive immunity of higher chordates. Due to the high specificity and sensitivity of this process, the immune system quickly recognizes and efficiently responds to the appearance of foreign and altered self-antigens. This is important for ensuring anti-infectious and antitumor immunity, in addition to maintaining self-tolerance. The most common parameter used for assessing the specificity of TCR-pMHC interaction is affinity. This thermodynamic characteristic is widely used not only in various theoretical aspects, but also in practice, for example, in the engineering of various T-cell products with a chimeric (CAR-T) or artificial (TCR-engineered T-cell) antigen receptor. However, increasing data reveal the fact that, in addition to the thermodynamic component, the specificity of antigen recognition is based on the kinetics and mechanics of the process, having even greater influence on the selectivity of the process and T lymphocyte activation than affinity. Therefore, the kinetic and mechanical aspects of antigen recognition should be taken into account when designing artificial antigen receptors, especially those that recognize antigens in the MHC complex. This review describes the current understanding of the nature of the TCR-pMHC interaction, in addition to the thermodynamic, kinetic, and mechanical principles underlying the specificity and high sensitivity of this interaction.

Enhanced expression of TNF-α type-1 receptors by immune cells in active pulmonary tuberculosis

BACKGROUND

Tumour necrosis factor-alpha (TNF-α) and its inhibitors are involved in both defence against tuberculosis (TB) and damage to the host by TB. Notably, the change in receptor expression on cell density is a key mechanism in regulation of the biological properties of cytokines.

OBJECTIVE

To study the differences in TNF-α receptor (TNFR) expression in patients with active pulmonary tuberculosis (aPTB) in correlation with the parameters of disease severity.

METHODS

TNFR1/2 levels on peripheral blood mononuclear cells (PBMCs) from 45 patients with aPTB and 150 healthy controls were analysed by flow cytometry using monoclonal antibodies and QuantiBRITE beads. Soluble TNFR1/2 and TNF-α in serum were measured using an enzyme-linked immunosorbent assay.

RESULTS

TNFR1 expression in aPTB patients was increased in the main populations of immune cells. Patients who were Mycobacterium tuberculosis culture-positive on bronchoscopy had higher levels of the soluble forms of TNFR1 (sTNFR1) than M. tuberculosis-negative patients.

CONCLUSION

Active TB was shown to cause activation of different immune cell types by increasing TNFR1 expression on cells and reducing sTNFR1 expression compared with healthy controls. M. tuberculosis-positive patients with disseminated infection had the highest sTNFR1 serum level compared with other patients, but did not differ in receptor expression on PBMCs.

The gene therapy of collagen-induced arthritis in rats by intramuscular administration of the plasmid encoding TNF-binding domain of variola virus CrmB protein

Wistar rats with collagen-induced arthritis were intramuscularly injected with the recombinant plasmid pcDNA/sTNF-BD encoding the sequence of the TNF-binding protein domain of variola virus CrmB protein (VARV sTNF-BD) or the pcDNA3.1 vector. Quantitative analysis showed that the histopathological changes in the hind-limb joints of rats were most severe in the animals injected with pcDNA3.1 and much less severe in the group of rats injected with pcDNA/sTNF-BD, which indicates that gene therapy of rheumatoid arthritis is promising in the case of local administration of plasmids governing the synthesis of VARV immunomodulatory proteins.

Tissue-specific expression of splice variants of human IL-4 and IL-6 gene mRNA

The spectrum of alternatively spliced IL-4 and IL-6 gene mRNA was studied in peripheral blood mononuclears from healthy donors and in human fetal tissues. It was found that the expression of alternatively spliced IL-4 and IL-6 gene mRNA in fetal tissues is tissue specific and that hemopoiesis- and immunopoiesis-related tissues differ by the amount of IL-4 and IL-4δ2 mRNA. An mRNA variant IL-4alt3 carrying partial exon 3 deletion was for the first time identified in human mononuclear cells.

[Phenotypic and functional characteristics of dendritic cells and contents of suppressor cell populations in peripheral blood of breast cancer patients]

The progression or the appearance of distant metastases in breast cancer (BC) is influenced by a variety of antitumor immune response suppression mechanisms. In this paper we study circulating dendritic cells (DC) and the suppressor cell populations in peripheral blood of breast cancer patients. The study of phenotypic and functional properties of DCs was performed in the samples of intact and TLR-stimulated whole blood from breast cancer patients and healthy women by multicolor flow cytometry. To determine the suppressor cell population among lymphocytes multicolor panel comprising markers CD 4, CD 25, CD 127, FoxP3 was used. It is showed that the formation of secondary foci of tumor growth in patients was accompanied by disturbances of the functional activity plasmocytoid DC and accumulation of cells with immunosuppressive functions.

Dendritic Cells Transfected with a DNA Construct Encoding Tumour-associated Antigen Epitopes Induce a Cytotoxic Immune Response Against Autologous Tumour Cells in a Culture of Mononuclear Cells from Colorectal Cancer Patients

Significant effort has been devoted to developing effective cancer vaccines based on dendritic cells (DCs) loaded with various tumour antigens, including DNA constructs that carry sequences of tumour-associated antigens (TAAs). Such vaccines efficiently and selectively activate the T cell immune response. In this study, we describe a method to induce an antitumour immune response in mononuclear cell (MNC) cultures from colorectal cancer patients using DNA-transfected DCs encoding TAA epitopes of carcinoembryonic antigen, epithelial cell adhesion molecule and mucin 4. DCs were obtained from peripheral blood monocytes of colorectal cancer patients. Magnetic-assisted transfection was used to deliver the genetic constructs to DCs. To assess the potency of the immune response, the antitumour cytotoxic response was assessed by lymphocyte intracellular perforin and the MNC cytotoxic activity against autologous tumour cells. We showed that polyepitope DNA-transfected DCs enhanced MNC antitumour activity, increasing tumour cell death and the percentage of perforin-positive lymphocytes. In addition, DNA-transfected DCs elicited a cytotoxic response that was as efficient as that of tumour lysate-loaded DCs. Taken together, the data suggest that it is feasible to induce an antitumour immune response in colorectal MNCs using transfected DCs. Thus, the DNA construct reported in this study may potentially be used in therapeutic and prophylactic DC-based vaccines.

[Features of functional activity of dendritic cells in tumor growth]

During recent years much data, accumulated on biology, function and role of dendritic cells (DC) in cancer development, in a new way allow assessing their role in disease process. Identification of features of DC functional state as well as their interaction and influence on the immune cells in tumor growth can be used as a basis for a new approach to cancer therapy enhancing standard therapy efficacy. The review analyzes different mechanisms of escaping of tumor cell from immune surveillance involving DC as one of the main participants of antitumor immune response. Also the prospects of using DC for vaccination are discussed. DC can be promising target for therapeutic strategies and also can be used for formation of antitumor response and cell therapy.

Biological effects of individually synthesized TNF-binding domain of variola virus CrmB protein

The biological characteristics of a 17-kDa protein synthesized in bacterial cells, a TNF-binding domain (VARV-TNF-BP) of a 47-kDa variola virus CrmB protein (VARV-CrmB) consisting of TNF-binding and chemokine-binding domains, were studied. Removal of the C-terminal chemokine-binding domain from VARV-CrmB protein was inessential for the efficiency of its inhibition of TNF cytotoxicity towards L929 mouse fibroblast culture and for TNF-induced oxidative metabolic activity of mouse blood leukocytes. The results of this study could form the basis for further studies of VARV-TNF-BP mechanisms of activity for prospective use in practical medicine.

Effect of mature dendritic cells primed with autologous tumor antigens from patients with epithelial ovarian cancer on stimulation of the cytotoxic immune response in culture of mononuclear cells

For modulation of antitumor cytotoxic activity of mononuclear cells in vitro, autologous dendritic cells loaded with tumor lysate antigens were cultured with peripheral blood mononuclear cells from patients with epithelial ovarian cancer in the presence or absence of IL-12 and IL-18. The efficiency of modulation was evaluated by cytotoxic activity of mononuclear cells against autologous tumor cells, by the production of IFN-γ, IL-4, and by the count of perforin-containing lymphocytes. It was demonstrated that dendritic cells stimulated cytotoxic immune response in mononuclear cell culture. Maximum induction of cytotoxic activity of mononuclear cells was attained in case of dendritic cells combination with IL-12 and IL-18 (increased death of autologous tumor cells, accumulation of perforin-positive lymphocytes, enhanced production of IFN-γ).

Production of TNF-α and IL-1β by peripheral blood mononuclear cells in carriers of different allele variants of the gene

Associations of cytokine production by mononuclear cells and the TNF-α genetic polymorphism in positions -238, -308, -376, -857, -1031, and of IL-1β in positions -31 and +3954 were studied. The data on distribution of allele and genotype incidence and on the level of spontaneous and mitogen-induced production of these cytokines by donor mononuclear cells demonstrated a statistically significant association of TNF-α production by mononuclear cells with polymorphic variants of the gene promoter regions -238>A (rs361525) and -857C>T (rs1799724). Carriers of -238GG/-308GG/-857CC/-1031NC genotype were characterized by low production of TNF-α, while carriers of -31TT/+3954CT genotype were characterized by low IL-1β stimulation index in response to mitogen in comparison with carriers of other genotype combinations.

Evaluation of the expression of isoforms of stem cell factor mRNA in fetal tissues and mononuclear cells at different stages of human development

We studied the expression of isoforms of stem cells factor mRNA forming as a result of alternative splicing. Both isoforms of stem cell factor mRNA forming as a result of alternative splicing were found in different fetal tissues. Changes in the expression of alternative isoforms of stem cell factor in peripheral blood mononuclear cells were demonstrated from the prenatal and neonatal periods to adult organism.

Restoration of hemopoiesis and immunopoiesis with small intestinal epitheliocytes in lethally irradiated mice

We studied hemopoiesis- and immunopoiesis-restoring activity of small intestinal epitheliocytes in lethally irradiated mice. The populations of peripheral blood cells and parameters of humoral and cellular immune response in lethally irradiated mice returned to normal 6 months after transplantation of cells from the small intestinal epithelial layer. Study of the distribution of intestinal cells in the body after transplantation showed long-term persistence of the donor cells in tissues of lethally irradiated animals. These data attest to high hemopoietic potential of small intestinal cells.

[Genetic and clinical and pathological characteristics of breast cancer in premenopausal and postmenopausal women]

This study involved 525 breast cancer (BC) patients of T2-4N0-2M0 stages at the age of 35 years and older. Significant differences in clinical and pathological characteristics between premenopausal and postmenopausal BC patients were found. Mostly marked differences were shown for positive lymph node correlation with distant metastasis, multicentric growth and local recurrence depending on menopause status. The prevalence of various morphological structures in primary tumors was appeared to be associated with different forms of tumor progression in pre- and postmenopausal women. We have studied polymorphisms in 15 genes involved in major cancer related pathways (apoptosis, interleukins, folate metabolism enzymes genes). We found that variant genotypes of MTHFR and DHFR genes were associated with an increased BC risk among premenopausal women while polymorphism in IL-18, p53 genes were associated with BC among postmenopausal women. These results demonstrate novel biological information, which points the different mechanisms contributed to breast cancer progression in premenopausal and postmenopausal women.

[Modulation of an antituberculous immune response in vitro, by using antigen-activated dendritic cells]

The protocol for preparation of mature antigen-activated dendritic cells (DC) from peripheral blood monocytes from patients with pulmonary tuberculosis was optimized. The obtained DCs were concurrently cultured with mononuclear cells (MNC) to activate antigen recognition, by and without adding IL-18 for the formation of directed differentiation of naive T cells to T helper cells type 1 (Th1). Joint cultivation of specific autologous DCs and MNCs from patients with pulmonary tuberculosis is an effective way of activation of the latter, which appeared as an increase in the proliferative potential, stimulation of IFN-gamma production and formation of cytotoxic cells expressing perforin in response to the specific Mycobacterium tuberculosis antigen ESAT-6. The use of recombinant IL-18 to enhance the induction of a Th1 response statistically significantly increases all the study parameters of MNC activation.

Proliferative activity of cells in mouse thymus and spleen under different diurnal regimens of interleukin-2 administration

Circadian variations in spontaneous and concanavalin A-stimulated proliferation of mouse thymocytes and splenocytes were studied after administration of recombinant interleukin-2 at different times of day. Differences were revealed in the effect of morning and evening treatment with the cytokine. The time of injection corresponded to various phases of the natural circadian rhythm of endogenous interleukin-2 production, which probably contributes to diurnal differences in the influence of this cytokine.

Alternative splicing of interleukin-6 mRNA in mice

Expression of mRNA for interleukin-6, interleukin-6Delta3, and interleukin-6Delta5 was detected in placental tissue (second and third trimesters of pregnancy) and spleen of mice immunized with sheep erythrocytes in high dose. We hypothesize that translation of mRNA yields proteins capable of binding to individual subunits of the interleukin-6 receptor and possessing effector functions.

Alternative splicing of murine interleukin-4 mRNA

We found an alternative form of mRNA with spliced second exon (IL-4delta2 mRNA) in mouse bone marrow and splenic cells. At rest, the amount of IL-4 mRNA markedly surpassed that of IL-4delta2 mRNA. Stimulation increased the content of both mRNA forms, but the alternative variant is accumulated more intensively and rapidly. We did not detect predominance of IL-4delta2 mRNA over full-length mRNA variant in the studied mouse tissues.

[Immunotropic properties of the causative agent of viral hepatitis C]

In this review the immunomodulating properties of the causative agent of viral hepatitis C are characterized on the basis of experimental data, obtained by Russian and foreign researchers during recent 3-5 years. The short characterization of the causative agent is presented and a number of adaptation mechanisms making it possible for hepatitis C virus to resist the action of the immune protective system of the host are considered. The role of individual protein products of the virus in the immunopathogenesis of the disease and the mechanisms of their action on the molecular level are discussed in detail on the basis of the results of mouse and in vitro experiments.

Effects of granulocyte-macrophage colony-stimulating factor produced by intestinal epithelial cells on functional activity of hemopoietic stem cells

The population of epithelial cells in the small intestine includes precursor cells of hemopoiesis possessing the ability to form splenic colonies on day 8. Intestinal epithelial cells stimulates proliferative and colony-forming activity of hemopoietic stem cells by producing granulocyte-macrophage colony-stimulating factor.

[Lymphocyte subpopulations and level of the proinflammatory cytokines in the blood of patients with hepatitis C and with combined variant of hepatitis C and B]

Subpopulation of cytotoxic lymphocytes CD8 having both secretory and cytolytic antiviral activity is supposed to play the essential role in the virus elimination. Inflammatory reactions are also of importance in the hepatitis C pathogenesis, their intensity being regulated by anti-inflammatory cytokins. This study was aimed at determination of lymphocyte subpopulation indices--the relative content of cells carrying markers CD4, CD8, CD16, CD19, CD72, the parameters of the phagocytic activity of granulocytes and monocytes, as well as serum concentrations of anti-inflammatory cytokines IL-1, IL-6 and TNF-alpha. These indices were evaluated in a group 132 patients with confirmed hepatitis C or mixed hepatitis B + C diagnosis, depending on the disease form and markers of the infectious process activity (as determined in the PCR test for hepatitis C virus RNA) in comparison with a group of healthy donors. In patients with variant hepatitis under study a growth in anti-inflammatory mediators concentration was observed along with decreased indices of lymphocyte subpopulations responsible for cell-mediated immunity and the phagocytosis parameters. In the case of mixed hepatitis these differences were shown to be more manifested.

[Analysis of polymorphism of the interleukin-4 gene of healthy and HIV-infected persons]

The distribution of the allel variants of the promoter area (C = 590T) of the interleukin-4 (IL-4) gene in HIV-infected and relatively healthy representatives of the Caucasoid population has been studied. The relationship between the genotypes of this polymorphism and the production of IL-4 by mononuclear cells of peripheral blood as well as distribution of IL-4 genotypes among males and females is analyzed. The occurrence of the homozygous combination of the allel variant C/C of the promoter of IL-4 has been shown to prevail almost twofold over the occurrence of the variant C/T among healthy donors and HIV-infected patients. Sexual differences play an essential role in the character of inheriting the allel variants of the genes of IL-4, the presence of the homozygous variant C/C or T/T being a risk factor of HIV infection in males. As revealed in this study, in the peripheral blood of healthy donors mononuclear cells having genotype C/C differ from cells with the heterozygous variant C/T in higher spontaneous production of IL-4 and, simultaneously, in lower capacity for the activation of its production in response to stimulation with mitogen. In HIV-infected patients mononuclear cells differ in higher spontaneous production of IL-4 in comparison with controls. We may thus infer that the human genotype controlling the initial level of the production of IL-4 by lymphocytes Th2 may influence the intensity of antibody production in the process of infection.

Production of cytokines by immature erythroid cells derived from human embryonic liver

It is well known that regulatory interactions between hematopoietic and lymphoid cells are mediated by different mediators. The cells of erythroid lineage are not an exception and have a regulatory effect on hemato- and immunopoiesis that can be mediated through the production of cytokines i.e. by soluble factors - a universal mechanism for cell regulation in hematopoietic and immune systems. It has been previously shown that erythroid progenitor cells from mice express mRNA of cytokines such as IL-1 alpha and beta, IL-4, IL-6, IFN-gamma, GM-CSF and TGF-beta. In this report we present the results of the production of the main immunoregulatory cytokines by erythroid cells derived from human embryonic liver. It was revealed that the cell population enriched with erythroid progenitors, isolated from human fetal liver, can produce IL-1 beta, IL-2, IL-4, IL-6. The levels of production of cytokines by immature erythroid progenitor cells is compared to the levels of corresponding cytokines produced by mitogen-stimulated peripheral blood mononuclear cells. The production of these cytokines changed quantitatively under the effect of erythropoietin, and are correlated with the expression of differentiation markers of erythroid cells such as AG-EB and Glycophorin A. The role of cytokine production by erythroid cells in hemato- and immunopoiesis and the mechanisms of self-regulation of proliferation and differentiation of erythroid progenitor cells is discussed.

[Level of Tx1- and Tx2-type cytokines in blood sera of hepatitis C patients]

The content of cytokines of type Tx1 (IL-2 and IFN-gamma) and type Tx2 (IL-4) in blood sera of 132 patients with hepatitis C and the combined form of hepatitis B + C was studied. For control, blood sera taken from healthy donors were used. A significant increase, in comparison with the control, in the content of IL-4 in all subgroups of the patients was registered. The content of IFN-gamma reached the maximum level in patients with acute hepatitis C with the positive result of the polymerase chain reaction (PCR) for the virus (216.4 and 46.4 pg/ml respectively) and was somewhat lower in acute hepatitis C with the negative PCR-result (77.7 and 9.6 pg/ml), mean while in the chronic course of hepatitis C these data were within the limits of control values irrespective of the results of PCR. In case of mixed infection in the acute clinical form a significant increase in the concentration of IFN-gamma (34.4 pg/ml) in comparison with the control (25.3 pg/ml) was observed. The content of IFN-gamma in patients with acute hepatitis C and the positive result of the test for NS antibodies also reached the maximum level (207.3 and 42.7 pg/mg respectively). But in contrast to hepatitis C in the acute form with the negative results of PCR in patients with hepatitis C in the acute form and the negative results of the NS test these data were within the limits of control values, as well as in the chronic course of hepatitis C irrespective of the results of the NS antibodies serum test. In case of mixed infection a significant increase in the concentration of IFN-gamma was registered in the subgroup of patients with the acute form of NS+ (39.9 pg/ml). The data obtained in this study were indicative of significant changes in the serum profile of serum cytokines of types Tx1 and Tx2 in different forms and courses of virus hepatitis. This makes it possible to believe that the chronization of the process was associated with the prevalence of the Tx2 function.

[The use of electrochemoluminescent method for detection of cytokines in various media]

Electrochemiluminescent (ECL) method was used for cytokine detection with TAG label (ruthenium(II) tris-bipyridine chelate N-hydroxysuccinimide ester). A quantitative ECL detection of IL-4 and IFN-gamma in physiological fluids and cell culture media is described. The results evidence that ECL is compatible to commercial kits or even more effective. The advantages of ECL are simple procedure, no need in washings, small volume of the assay, wide range of cytokine concentrations, high sensitivity, and good reproducibility. The method can be used in research and clinical laboratories.

Regulation of functional activity of bone marrow hemopoietic stem cells by erythroid cells in mice

Transplantation of erythroid and bone marrow cells to irradiated mice stimulated exogenous colony formation. Pretreatment of erythroid cells with specific rabbit antiserum to erythroblasts abolished this effect. The reverse transcriptase polymerase chain reaction revealed the presence of mRNA for interleukin-1alpha, interleukin-1beta, interleukin-3, interleukin-6, and granulocyte-macrophage colony-stimulating factor in erythroid cells. Granulocyte-macrophage colony-stimulating factor was found in the conditioned medium from erythroid cells. Thus, erythroid cells stimulated colony-forming activity of bone marrow cells, which was probably mediated via cytokine synthesis (e.g., granulocyte-macrophage colony-stimulating factor).

Characterization of erythroid cell-derived natural suppressor activity

Nucleated erythroid cells (NEC) have been previously reported to the capable of suppressing antibody-mediated primary (IgM) and secondary (IgG) immune responses to thymus-dependent antigens. In the present study we indicated that NEC, separated from the spleens of mice following phenylhydrazine treatment were able to suppress directly the proliferative response of preactivated B cells to lipopolysaccharide (LPS) in vitro. While being active in suppressing B cell blastogenesis, NEC, however, failed to reduce both cell proliferation and cytotoxic T lymphocyte (CTL) generation in an allogeneic mixed lymphocyte culture (MLC). NEC also lacked a significant effect on interleukin (IL)-2 production and utilization by concanavalin A (Con A)-activated T lymphocytes. The NEC-derived suppression of B cell proliferation was, at least in part, mediated by soluble molecules. The specific blockade of transforming growth factor (TGF)-beta synthesis with antisense oligodeoxynucleotides (OD) binding TGF-beta mRNA, as well as the neutralization of TGF-beta activity with anti-TGF-beta antibodies (Ab), resulted in a detectable diminished ability of the NEC-conditioned medium (CM) to suppress B cell blastogenesis. Taken together, the results suggest that: 1) NEC may suppress directly B cell responses, while not affecting T cell ones; 2) NEC may mediate their natural suppressor (NS) activity partially through releasing TGF-beta.

[The use of antisense oligonucleotides for modulation of cytokine gene expression]

The review summarizes literature data on the mechanism of action and the use of antisence oligonucleotides for modulation of cytokine gene expression in haemo- and immunopoesis. This new approach for gene-directed modulation of the gene expression allows to analyze both intercellular and intracellular protein interaction. Use of this approach is prospective for both experimental researches in vivo and in vitro and application in therapeutic purposes.

Cytokine gene expression in erythroid cells

Erythroid nuclear cells have been shown to exert regulatory effects on immunopoiesis. We have reported that some of these influences might be mediated via soluble factors secreted by nuclear erythroid cells. In this report we describe our estimate of the cytokine gene expression in cells isolated from individual erythroid colonies by Reverse transcription-Polymerase chain reaction. We found in erythroid cells, originated from the bone marrow precursors obtained from phenylhydrazine-treated mouse, the expression of the following cytokine genes: IL-1 alpha and IL-1 beta, IL-4, IL-6, GM-CSF, gamma-IFN and TGF-beta. In contrast, the erythroid cells derived from newborn mouse spleen precursor cells expressed IL-1 alpha, IL-1 beta, IL-4, IL-6 and GM-CSF mRNAs but not gamma-IFN and TGF-beta mRNAs. No detectable levels of IL-2, IL-3 and IL-5 mRNAs were expressed in nuclear erythroid cells. These data provide evidence of the expression of mRNAs coding in the set of immunoregulatory cytokines in immature erythroid progenitor cells in mouse.