Cellular allo reactivity against paternal HLA antigens in normal multiparous females as detected by intracellular cytokine flow cytometry remains elevated over years despite diminution of anti-HLA antibody levels

The expression of human leukocyte antigen by human ejaculated spermatozoa

Background

After coitus and insemination, an inflammatory response is evident in the female reproductive tract (FRT). Semen contains a variety of immune‐activating components that have a major role in the induction of an immune response in the FRT. One of the most important is (human leukocyte antigen) HLA molecules which are present in soluble form in seminal plasma and in membrane form on the surface of cells (such as epithelial and leukocytes) existing in semen. Nevertheless, there is considerable debate over the expression of HLA antigens by human spermatozoa. Considering the critical role of HLA molecules in reproduction and the induction of an immune response, it is very important to clearly define HLA expression by spermatozoa and the role of these molecules in sperm morphology, motility, and strength to fertilize an egg. Therefore, the objective of this study was to determine HLA expression by ejaculated spermatozoa. The results of this study will facilitate the design of future studies.

Method

Semen samples were collected from 50 healthy men with normal semen status by masturbation after 2–3 days of sexual abstinence. After purification of normal spermatozoa, HLA class I & II expression was evaluated by quantitative real‐time PCR and flow cytometry methods.

Results

The results showed the expression of both HLA class I & class II by spermatozoa. The results also showed that the expression of HLA class Ⅱ was significantly more than HLA class Ⅰ.

Conclusion

Spermatozoa express both HLA class I & class II molecules.

Tocilizumab (Anti-IL-6R) Suppressed TNFα Production by Human Monocytes in an In Vitro Model of Anti-HLA Antibody-Induced Antibody-Dependent Cellular Cytotoxicity

Background

We previously demonstrated that natural killer (NK) cells activated via FcγRIIIa (CD16) interactions with anti-HLA antibodies binding to peripheral blood mononuclear cells (PBMCs) in the in vitro antibody-dependent cellular cytotoxicity (ADCC) assay produced IFNγ. Here we investigate if other CD16 bearing cells are responsive to alloantigen via alloantibody in the in vitro ADCC and if the ADCC-induced cytokine reactions and cytotoxicity can be modified by the anti-interleukin 6 receptor (IL-6R) monoclonal antibody, Tocilizumab (TCZ).

Methods

Whole blood from a normal individual was incubated overnight with irradiated allo-PBMCs pretreated with anti-HLA antibody positive (in vitro ADCC) or negative sera (mixed lymphocyte reaction [MLR]), with or without TCZ or control IgG. IFNγ+, TNFα+ or IL-6+ cell% in NK cells, monocytes and CD8+ T cells were enumerated by cytokine flow cytometry. ADCC using PBMCs (effector) and Farage B cells (FB, target) with anti-HLA antibody positive sera, with or without TCZ, was measured by flow cytometry.

Results

IFNγ+ and/or TNFα+ cell% in NK cells, monocytes and CD8+ T cells were elevated in the ADCC compared to the MLR condition. IL-6+ cells were significantly increased in ADCC versus MLR (10.2 ± 4.8% vs 2.7 ± 1.5%, P = 0.0003), but only in monocytes. TCZ treatment significantly reduced TNFα+ cell% in monocytes in ADCC, but had no effect on other cytokine+ cells. TCZ showed no effect on cytotoxicity in ADCC.

Conclusions

IFNγ, TNFα, and IL-6 production induced by HLA antibody-mediated CD16 bearing cell activation in NK cells, monocytes, and CD8+ T cells suggests a potential role for ADCC and these inflammatory cytokines in mediation of antibody-mediated rejection. TCZ suppressed TNFα production in monocytes in the ADCC condition, suggesting a role of IL-6/IL-6R pathway in monocytes activation. Inhibition of this pathway could reduce the inflammatory cascade induced by alloantibody, although the inhibitory effect on cytotoxicity is minimal.

The Role of Natural Killer Cells in Humoral Rejection

Antibody-mediated rejection (AMR) has been identified among the most important factors limiting long-term outcome in cardiac and renal transplantation. Therapeutic management remains challenging and the development of effective treatment modalities is hampered by insufficient understanding of the underlying pathophysiology. However, recent findings indicate that in addition to AMR-triggered activation of the classical complement pathway, antibody-dependent cellular cytotoxicity by innate immune cell subsets also promotes vascular graft injury. This review summarizes the accumulating evidence for the contribution of natural killer cells, the key mediators of antibody-dependent cellular cytotoxicity, to human AMR in allotransplantation and xenotransplantation and illustrates the current mechanistic conceptions drawn from animal models.

Genes associated with antibody-dependent cell activation are overexpressed in renal biopsies from patients with antibody-mediated rejection

INTRODUCTION

Antibody-mediated rejection (ABMR) is dependent on complement activating donor-specific anti-HLA antibodies (DSA). This is commonly detected by C4d deposition in allografts. However, recent data define a C4d negative ABMR phenotype suggesting a role for complement-independent DSA injury, antibody-dependent cellular cytotoxicity (ADCC).

METHODS

Here, we established an in vitro ADCC model that identified human ADCC-activated genes using microarray analysis. We subsequently interrogated renal allograft biopsies from patients with ABMR and controls for mRNA expression of the ADCC-activated gene set.

RESULTS

We identified 13 ADCC-activated genes. Six gene expression assays including 8 of the 13 genes (CCL3, CCL4/CCL4L1/CCL4L2, CD160, IFNG, NR4A3 and XCL1/XCL2) were analyzed in 127 kidney biopsies obtained from HLA-sensitized (HS), non-HS patients and control individuals. Most ADCC-activated genes showed significantly higher expression in the transplant samples compared to the controls (p<0.0005). The gene expression levels were significantly higher in HS and non-HS transplant patients who developed ABMR compared to those who did not (p=0.04-0.002). There was no difference in the gene expression levels between C4d positive and negative ABMR (p=0.26-0.99). Samples from high PRA (>80%) or positive DSA patients showed higher gene expression levels for the ADCC-activated genes compared to low PRA (<80%) and negative DSA patients (p=0.04-0.001).

CONCLUSION

ADCC pathways are active in transplant patients with ABMR, and likely mediate allograft injury, providing a potential mechanism for C4d negative ABMR.

Characterization of transfusion-elicited acute antibody-mediated rejection in a rat model of kidney transplantation

Animal models of antibody-mediated rejection (ABMR) may provide important evidence supporting proof of concept. We elicited donor-specific antibodies (DSA) by transfusion of donor blood (Brown Norway RT1(n) ) into a complete mismatch recipient (Lewis RT1(l) ) 3 weeks prior to kidney transplantation. Sensitized recipients had increased anti-donor splenocyte IgG1, IgG2b and IgG2c DSA 1 week after transplantation. Histopathology was consistent with ABMR characterized by diffuse peritubular capillary C4d and moderate microvascular inflammation with peritubular capillaritis + glomerulitis > 2. Immunofluorescence studies of kidney allograft tissue demonstrated a greater CD68/CD3 ratio in sensitized animals, primarily of the M1 (pro-inflammatory) phenotype, consistent with cytokine gene analyses that demonstrated a predominant T helper (TH )1 (interferon-γ, IL-2) profile. Immunoblot analyses confirmed the activation of the M1 macrophage phenotype as interferon regulatory factor 5, inducible nitric oxide synthase and phagocytic NADPH oxidase 2 were significantly up-regulated. Clinical biopsy samples in sensitized patients with acute ABMR confirmed the dominance of M1 macrophage phenotype in humans. Despite the absence of tubulitis, we were unable to exclude the effects of T cell-mediated rejection. These studies suggest that M1 macrophages and TH 1 cytokines play an important role in the pathogenesis of acute mixed rejection in sensitized allograft recipients.

Regulation of anti-HLA antibody-dependent natural killer cell activation by immunosuppressive agents

BACKGROUND

It was demonstrated that human natural killer (NK) cells, via antibody-dependent cellular cytotoxicity (ADCC)-like mechanism, increase IFNγ production after exposure to alloantigens. This finding was associated with an increased risk for antibody-mediated rejection (ABMR). Although the effects of various immunosuppressive drugs on T cells and B cells have been extensively studied, their effects on NK cells are less clear. This study reports the effect of immunosuppressive agents on antibody-mediated NK cell activation in vitro.

METHODS

Whole blood from normal individuals was incubated with irradiated peripheral blood mononuclear cells (PBMCs) pretreated with anti-HLA antibody+ sera (in vitro ADCC), with or without immunosuppressive agents. The %IFNγ+ and CD107a+ (degranulation marker) in CD56+ NK cells were enumerated by flow cytometry.

RESULTS

Cyclosporine A and tacrolimus significantly reduced IFNγ production in a dose-dependent manner (53%-83%), but showed minimal effect on degranulation (20%). Prednisone significantly reduced both IFNγ production and degranulation (50%-66% reduction at maximum therapeutic levels). Calcineurin inhibitors (CNIs) in combination with prednisone additively suppressed IFNγ production and degranulation. The effect of sirolimus or mycophenolate mofetil on NK cells was minimal.

CONCLUSIONS

These results suggest that potent suppressive effects of CNIs and prednisone on antibody-mediated NK cell activation may contribute to the reduction of ADCC in sensitized patients and possibly reduce the risk for ADCC-mediated ABMR. These further underscore the importance of medication compliance in prevention of ABMR and possibly chronic rejection, and suggest that ADCC-mediated injury may increase in strategies aimed at CNI or steroid minimization or avoidance.