Heterogeneity of antigen specificity between HLA-A*02:01 and other frequent Chinese HLA-A2 subtypes detected by a modified autologous lymphocyte-monocyte coculture

HLA-A2 is the most common serological HLA type among all ethnic groups. Through advances in DNA typing, more than 800 subtypes of HLA-A2 have been identified, and the existence of heterogeneity of antigen specificity among the HLA-A2 subtypes has been suggested by retrospective analyses of allogeneic transplantation patients and by studies of antigen amino acid structure. However, prior to this study, the antigenicity of a given subtype or the mismatch extent between two given subtypes could not be studied in vitro. Here, we used a modified autologous lymphocyte-monocyte coculture method to reveal heterogeneity of antigen specificity among HLA-A2 subtypes. The coculture was set up with HLA-A2 (non-A*02:01) lymphocytes and monocytes, and the monocytes were coated with an HLA-A*02:01/IgG1-Fc fusion protein (dimer) by high-affinity binding of the IgG1-Fc to FcgRI. Lymphocyte proliferation following coculture indicated that HLA-A*02:01 showed antigenicity against the HLA-A2 (non-A*02:01) subtype. Among the most frequent HLA-A2 subtypes in the Chinese population (HLA-A*02:01, -A*02:03, -A*02:06 and -A*02:07), we identified significant -A*02:01 antigenicity for T cells from -A*02:03 or -A*02:06 but not -A*02:07 individuals. Our findings were consistent with retrospective studies of allograft patients with a limited number of involved subtypes, indicating that this modified coculture method provides a practical and reliable means to study the antigenicity of HLA allele subtypes in vitro.

Puerarin alleviates delayed-type hypersensitivity via cytokine inhibition by modulating Th1/Th2 balance

Puerarin has long been used as a traditional Chinese medicine, which possesses various physiological properties, including anti-inflammation, anti-oxidative, anti-diabetic and anti-cancer activities. The aim of the current study was to investigate the effect of puerarin on delayed-type hypersensitivity (DTH) induced by ovalbumin (OVA) in mice and explore its underlying mechanisms. The results showed that puerarin significantly attenuated DTH, resulting from a decrement in footpad swelling, reduction in inflammatory cell as well as a decline in anti-OVA IgG in serum. In the homogenized supernatant of footpad tissues, the classic Th1-cytokines, including interferon (IFN)-γ was suppressed following puerarin treatment. Furthermore, a high dose of puerarin inhibited interleukin (IL)-4 production, the classic Th2-cytokine. The concanavalin A stimulation and MTT assays indicated a suppressive effect of puerarin on Th1 response via decreasing IFN-γ production in OVA-primed lymphocytes. Detailed studies revealed that puerarin modulated the Th1/Th2 balance in DTH responses, attributing to lower T-bet/GATA binding protein-3 mRNA and protein level ratios, which led to the shift change of IFN-γ/IL-4 with puerarin treatment. These findings demonstrate that puerarin alleviated inflammation in DTH triggered by OVA application via curbing inflammatory cytokines by modulating the Th1/Th2 balance. These results suggest that puerarin may be an alternative therapeutic option for the treatment of DTH.

A similarity in peptide cross-reactivity between alloantigen- and nominal antigen-induced CD8+ T cell responses in vitro

Raising tumor-specific allorestricted T cells in vitro for adoptive transfusion is expected to circumvent host tumor tolerance. However, it has been assumed that alloreactive T cell clones activated in vitro ranges from peptide-specific with high avidity to peptide-degenerate with low avidity. In this study, we examined the peptide specificity and cross-reactivity of T cell responses in vitro to an allogeneic epitope and a nominal epitope with a modified co-culture of lymphocytes and autologous monocytes. After binding to the monocyte via the interaction of its Fc part and the cell surface IgG Fc receptor type I (FcγRI), a fusion protein consisting of the extracellular domains of HLA-A2 molecule and the Fc region of IgG1 (the dimer) introduced a single epitope into the co-culture. The dimer-coated monocytes stimulated the proliferation of autologous CD8(+) T cells after co-culturing. The CD8(+) T cell responses were self-HLA-restricted for HLA-A2-positive (HLA-A2+ve) samples and allo-HLA-restricted for HLA-A2-negative (HLA-A2-ve) samples, since the co-cultural bulks stained with HLA-A2 tetramers, human interferon-gamma (IFN-γ) production in response to T cell receptor (TCR) ligands, and cytotoxicity against a panel of target cells exhibited peptide-specific properties. Two HLA-A2-restricted peptides with sequence homology were included, allowing the comparison of cross-reactivity between allo-antigen- and nominal antigen-induced CD8(+) T cell responses. Interestingly, the allo- and self-HLA-restricted CD8(+) T cell responses were similar in the peptide cross-reactivity, although the allorestricted T cell response seemed, overall, more intensive and had higher binding affinity to specific tetramer. Our findings indicated the alloreactive T cells raised by the co-culture in vitro were as peptide specific and cross-reactive as the self-HLA-restricted ones.

Tumor rejection effects of allorestricted tumor peptide-specific CD4(+) T cells on human cervical cancer cell xenograft in nude mice

Generation of tumor specific alloreactive CD4(+) T cells is important to circumvent tumor tolerance. Here, we generate allorestricted peptide-specific CD4(+) T cells by coculture of lymphocytes and autologous monocytes bearing allogeneic HLA-DR15 molecule associated with its restricted peptide. Binding of a dimeric HLA-DR15/IgG1-Fc fusion protein (the dimer) to HLA-DR15 negative (HLA-DR15-ve) monocytes made the monocytes coated with the allogeneic epitope. An increased proliferation of CD4(+) T cells and induction of Th1 cells appeared after coculturing of HLA-DR15-ve lymphocytes and the autologous monocytes loaded with the dimer. The cocultural bulks showed an increased frequency of the specific dimer-stained CD4(+) T cells and the expanded CD4(+) T cells exhibited an elevated IFN-γ production in response to specific TCR ligand. Tumor rejection effects of the allorestricted E7-specific CD4(+) T cells raised by the coculture were observed in nude mice challenged with human cervical cancer cell SiHa expressing both HLA-DR15 and E7 antigens, as the tumor avoidance and life span of the mice were improved after adoptive transfer of the CD4(+) T cells. This study may help to develop strategies to separate graft-versus-leukemia or graft-versus-tumor reaction from graft-versus-host disease, and add to the pool of human high-avidity TCRs specific for tumor or virus antigens.

Barriers of the Human Organism and Their Achilles’ Heels

The human body is covered by barriers separating it from the external and internal surroundings. The “milieu enterieur” has to be stabilised in spite of the variable external and internal conditions of toxic, osmotic, microbial and climatic environmental circumstances. This first line of barriers is composed of skin and mucous membranes of complicated structures.

A second line of barrier system is present in our organisms. Certain organs have to be separated from the immune system and other parts of the body because of evolutionary reasons (eye-bulb and testicles) because of unique proteins “unknown” for the acquired immune system. The blood-brain barrier (BBB) is providing enhanced safety circumstances for the central nervous system. The second line of barriers is represented by the special properties of the capillary endothelial system.

The maternal-fetal barrier is the most complex. At the maternal fetal interface two individuals of two different haplotypes has to be live 9 months separated by a very complicated dynamic barrier.

The placenta is the organ, which is separating the maternal and fetal tissues. Similar to others the bidirectional transport of gasses, metabolites, cells, proteins, regulatory substances, are transported by active or passive transcellular and intercellular mechanisms.

The fetal immune system develops immunotolerance to all maternal cells and antigens transferred transplacentally. The problem is to mitigate the maternal immune system to tolerate the paternal haplotype of the fetus. In the case of normal pregnancy a complex series of physiological modifications can solve the problem without harmful consequences to the mother and fetus.

The outermost contact cells of trophoblasts express instead of HLA-class Ia and class II antigens non-variable HLA-C, HLA-E, HLA-F and HLA-G antigens. The first consequence of this is reduction of the activity of maternal natural killer cells and maternal dendritic cells;

Progesteron, micro-RNA and mediators influence the development of T effector-cells. The production of soluble HLA-G(5 and 6) and IL-10 supports the differentiation of Th-2 CD4⁺ helper cells, reducing the ability of maternal cells to kill fetal cells.

Series of receptors and costimulators are expressed by the different lines of semi-allogenic trophoblast cells to bind HLA-G and mitigate maternal immune response;

The maternal immunotolerance is further facilitated by the activation of CD4⁺CD25^brightFoxp3⁺ regulatory T (T_REG) cells.

Infections have to be prevented during pregnancy. The cells of placenta express 10 Toll-like receptors a group of pattern recognition receptors responsible for innate immunity. The interferon level is also higher in the placental tissues than in the somatic fetal or maternal cells.

The complement system is also adapted to the requirements of the pregnancy and fetal damage is inhibited by the production of “assymmetric IgG antibodies” under hormonal and placental-regulation. These modifications prevent the activation of complement, cytotoxic activity, opsonising ability, antigen clearance and precipitating activity of the molecules.

The Achilles’ heels of the different barriers are regularly found by virus infections. Lamina cribrosa of the blood-brain barrier, optical nerve of the eyes, etc. the risk factors of the maternal-fetal barrier has been summarised in Table 1.1.

Killer artificial antigen-presenting cells: the synthetic embodiment of a 'guided missile'

At present, the treatment of T-cell-dependent autoimmune diseases relies exclusively on strategies leading to nonspecific suppression of the immune systems causing a substantial reduced ability to control concomitant infections or malignancies. Furthermore, long-term treatment with most drugs is accompanied by several serious adverse effects and does not consequently result in cure of the primary immunological malfunction. By contrast, antigen-specific immunotherapy offers the potential to achieve the highest therapeutic efficiency in accordance with minimal adverse effects. Therefore, several studies have been performed utilizing antigen-presenting cells specifically engineered to deplete allo- or antigen-specific T cells ('guided missiles'). Many of these strategies take advantage of the Fas/Fas ligand signaling pathway to efficiently induce antigen-presenting cell-mediated apoptosis in targeted T cells. In this article, we discuss the advantages and shortcomings of a novel non-cell-based 'killer artificial antigen-presenting cell' strategy, developed to overcome obstacles related to current cell-based approaches for the treatment of T-cell-mediated autoimmunity.