Examination of IgG Fc Receptor CD16A and CD64 Expression by Canine Leukocytes and Their ADCC Activity in Engineered NK Cells.

Human natural killer (NK) cells can target tumor cells in an antigen-specific manner by the recognition of cell bound antibodies. This process induces antibody-dependent cell-mediated cytotoxicity (ADCC) and is exclusively mediated by the low affinity IgG Fc receptor CD16A (FcγRIIIA). Exploiting ADCC by NK cells is a major area of emphasis for advancing cancer immunotherapies. CD64 (FcγRI) is the only high affinity IgG FcR and it binds to the same IgG isotypes as CD16A, but it is not expressed by human NK cells. We have generated engineered human NK cells expressing recombinant CD64 with the goal of increasing their ADCC potency. Preclinical testing of this approach is essential for establishing efficacy and safety of the engineered NK cells. The dog provides particular advantages as a model, which includes spontaneous development of cancer in the setting of an intact and outbred immune system. To advance this immunotherapy model, we cloned canine CD16A and CD64 and generated specific mAbs. We report here for the first time the expression patterns of these FcγRs on dog peripheral blood leukocytes. CD64 was expressed by neutrophils and monocytes, but not lymphocytes, while canine CD16A was expressed at high levels by a subset of monocytes and lymphocytes. These expression patterns are similar to that of human leukocytes. Based on phenotypic characteristics, the CD16A+ lymphocytes consisted of T cells (CD3+ CD8+ CD5dim α/ß TCR+) and NK cells (CD3- CD5- CD94+), but not B cells. Interestingly, the majority of canine CD16A+ lymphocytes were from the T cell population. Like human CD16A, canine CD16A was downregulated by a disintegrin and metalloproteinase 17 (ADAM17) upon leukocyte activation, revealing a conserved means of regulation. We also directly demonstrate that both canine CD16A and CD64 can induce ADCC when expressed in the NK cell line NK-92. These findings pave the way to engineering canine NK cells or T cells with high affinity recombinant canine CD64 to maximize ADCC and to test their safety and efficacy to benefit both humans and dogs.

Microcirculatory Improvement Induced by Laparoscopic Sleeve Gastrectomy Is Related to Insulin Sensitivity Retrieval.

AIMS: Microvascular dysfunction is a potential factor explaining the association of obesity, insulin resistance, and vascular damage in morbidly obese subjects. The purpose of the study was to evaluate possible determinants of microcirculatory improvement 1 year after laparoscopic sleeve gastrectomy (LSG) intervention. METHODS: Thirty-seven morbidly obese subjects eligible for bariatric surgery were included in the study. Post-occlusive reactive hyperemia (PORH) of the forearm skin was measured as area of hyperemia (AH) by laser-Doppler flowmetry before LSG and after a 1-year follow-up. RESULTS: After intervention, we observed a significant reduction in BMI, HOMA index, HbA1c, and a significant increase of AH in all patients after surgery; this variation was significant only in those patients having insulin resistance or prediabetes/diabetes. Although significant correlation between the increase of AH and the reduction of both BMI, HOMA index, and HbA1c was observed, BMI was the only independent predictor of AH variation after LSG at the linear regression analysis. CONCLUSIONS: Our study shows that LSG intervention is correlated with a significant improvement in the microvascular function of morbidly obese subjects; this improvement seems to be related to the baseline degree of insulin-resistance and to the retrieval of insulin-sensitivity post-intervention.