Aldo Misefari

Susceptibility of Human Melanoma Cells to Autologous Natural Killer (NK) Cell Killing: HLA-Related Effector Mechanisms and Role of Unlicensed NK Cells

Background Despite Natural Killer (NK) cells were originally defined as effectors of spontaneous cytotoxicity against tumors, extremely limited information is so far available in humans on their capability of killing cancer cells in an autologous setting. Methodology/Principal Findings We have established a series of primary melanoma cell lines from surgically resected specimens and here showed that human melanoma cells were highly susceptible to lysis by activated autologous NK cells. A variety of NK cell activating receptors were involved in killing: particularly, DNAM-1 and NKp46 were the most frequently involved. Since self HLA class I molecules normally play a protective role from NK cell-mediated attack, we analyzed HLA class I expression on melanomas in comparison to autologous lymphocytes. We found that melanoma cells presented specific allelic losses in 50% of the patients analyzed. In addition, CD107a degranulation assays applied to NK cells expressing a single inhibitory receptor, revealed that, even when expressed, specific HLA class I molecules are present on melanoma cell surface in amount often insufficient to inhibit NK cell cytotoxicity. Remarkably, upon activation, also the so called “unlicensed” NK cells, i.e. NK cells not expressing inhibitory receptor specific for self HLA class I molecules, acquired the capability of efficiently killing autologous melanoma cells, thus additionally contributing to the lysis by a mechanism independent of HLA class I expression on melanoma cells. Conclusions/Significance We have investigated in details the mechanisms controlling the recognition and lysis of melanoma cells by autologous NK cells. In these autologous settings, we demonstrated an efficient in vitro killing upon NK cell activation by mechanisms that may be related or not to abnormalities of HLA class I expression on melanoma cells. These findings should be taken into account in the design of novel immunotherapy approaches against melanoma.

HUMAN LEUKOCYTE ANTIGEN FREQUENCY IN HUMAN HIGH-GRADE GLIOMAS: A CASE-CONTROL STUDY IN SICILY

OBJECTIVEHuman leukocyte antigens (HLAs) are widely expressed cell surface molecules that present antigenic peptides to T lymphocytes and modulate immune response against inflammatory and malignant diseases. The aim of this study was to compare HLA distribution in patients with newly diagnosed high-grade gliomas (HGGs) and 2 control groups from a restricted geographic area (eastern Sicily). METHODSHLA allele frequency, as determined from peripheral blood of 56 adult patients with HGGs, was compared with that of 2 different control groups: 140 healthy bone marrow donors (group A) and 69 virtually brain tumor–free patients (group B). HLA expression was evaluated using a reverse transcriptase polymerase chain reaction–sequence-specific oligonucleotide probe. RESULTSThere was significant expression of HLA-A*11 in patients with HGGs compared with control groups A and B (P < 0.003 and P < 0.018, respectively). Significant expression of HLA genotypes in patients with HGGs was also identified for HLA-DQB1*06 (P = 0.005), HLA-DRB1*14 (P = 0.001), and HLA-DRB3*01 (P = 0.007) compared with control group B. In HGG patients, there was statistically significantly decreased expression, compared with control groups A and B, of HLA-B*07 (P = 0.002 and P = 0.03, respectively) and HLA-C*04 (P = 0.007 and P = 0.016, respectively). There was statistically significant lower expression of HLA-C*05 in the HGG group compared with group B (P < 0.03). CONCLUSIONThis is the first study to describe the frequency of distribution of HLAs in a population from a restricted geographic area. The findings suggest a possible correlation between HLA allele distribution and the occurrence of newly diagnosed malignant astroglial brain tumors.

Effect of prostaglandin E2 on pokeweed mitogen-activated human lymphocyte cultures

It is shown that a short incubation of peripheral human lymphocytes with PGE2 is able to reduce the B cell differentiation induced by PWM. The target of PGE2 action appears to belong to T lymphocytes, since the treatment of non-T cells is uneffective in reducing the immune response. Both OKT4+ and OKT8+ subsets are sensitive to PGE2. Data concerning the role of endogenous as well as exogenous PGE2 either on unfractionated or fractionated OKT4+, OKT8+ and non-T lymphocytes are also discussed. The PGE2 inhibition on immunoglobulin synthesis in PWM-stimulated cultures seems to be mediated by a complex effect on both the T cell subsets.

Prostaglandin E2-induced inhibition of the in vitro immune response by SRBC-stimulated human lymphocytes.

Exogenous PGE2 strongly inhibits the response of human lymphocyte cultures to SRBC. This effect is mediated through a T cell inhibition since non-T cells are not significantly affected. Indomethacin, which inhibits in this system lymphocyte endogenous PGE2 synthesis increases the in vitro immune response. The effect of indomethacin is overcame by exogenous PGE2. These data may be relevant for explaining the immunomodulatory role of PGE2 following antigen challenge.

Effect of prostaglandins on Fc-IgG receptors of human circulating T and B lymphocytes

A short preincubation of human T and B lymphocyte subpopulations with physiologic or pharmacologic concentrations of PGs E2 and F1 alpha, but not with E1 and F2 alpha, markedly depresses the cell ability to bind immune complexes, through FcR-IgG. This effect appears to be relatively temperature-independent. These observations indicate that PG treatment of human lymphocytes may be useful to distinguish the subclasses of FcR-IgG-bearing T and B cells, which are sensible to the modulating effect of PGs.

Anti-LPS region antibody responses and cellular immune responsiveness in typhoid patients

In recent years, several reports have provided evidence for an involvement of the immune system during typhoid fever (3). In particular, a reduction of several immunological parameters such as leukocyte inhibiting factor (LIF) release, plaque-forming cell (PFC) production and natural killer (NK) cell activity have been demonstrated (1). In addition, Salmonella typhi organisms possess on their outermembrane the lipopolysaccharide (LPS) which is a powerful immunomodulating agent (4). Therefore, to better investigate the relationship between immune function and typhoid fever, we analyzed humoral and cell-mediated responses in typhoid patients towards LPS or whole bacteria.

Effect of Cyclooxygenase Inhibitors on PGE2 -Sensitive Human Lymphocyte Receptors

A short preincubation of human T and B lymphocyte populations with exogenous Prostaglandin E2 (PGE2) markedly depresses the expression of surface receptors binding the Fc portion of IgG, sheep and mouse erythrocytes (FcR-IgG, Ea and ME receptors respectively). Using two cyclooxygenase inhibitors (indomethacin and meclofenamate) it is shown that endogenous PGE2 does not modify the activity of these lymphocyte surface receptors. The lymphocyte sensitivity to exogenous PGE2, which is released under various physiologic and pathologic stimuli, may represent present another method to subdivide human lymphocytes in distinct subsets.