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

OBJECTIVE

Human 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).

METHODS

HLA 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.

RESULTS

There 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).

CONCLUSION

This 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.

Interleukin-12 and interleukin-10 production by mononuclear phagocytic cells from breast cancer patients

Interleukin-10 (IL-10) and Interleukin 12 (IL-12) generation may be regulated by a complex monocyte and macrophage-derived cytokine network and an impairment of the immune system can be observed in neoplastic disease. In this study, we examined the production of these cytokines by phagocytic cells, obtained from breast cancer (BCa)-bearing patients. Our results suggest that an increased IL-10 formation may represent an important regulatory pathway of IL-12 production by BCa mononuclear cells. In this report, we show that mononuclear cells of patients affected by breast cancer have a defective IL-12 production capability while generating higher amounts of IL-10.

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.

Senile dementia, Alzheimer type: a distinct entity in the immunosenescence?

Since previous data have provided conflicting results on immunoresponsiveness in senile dementia, Alzheimer type (SDAT), we evaluated the immune function in groups of SDAT patients and aged and young donors. In comparison to the younger subjects, SDAT and aged subjects did not exhibit significant differences in lymphocyte surface markers. Both groups of aged donors showed decreased B cell polyclonal responsiveness in a nonspecific T cell-driven B lymphocyte differentiation system. The use of an antigen-specific induction assay revealed an imbalance of T helper (Th) or T suppressor function in the elderly, while SDAT individuals were characterized by decreased Th activity. At the same time, aged individuals manifested an impairment of leukocyte-inhibiting factor (LIF) and lymphocyte-derived chemotactic factor production; a selective deficit of LIF release was seen in SDAT. Finally, elderly individuals displayed a decline of polymorphonuclear cell (PMN)-mediated functions and monocyte phagocytosis; only a decrease in PMN response was observed in SDAT. These results reveal discrepancies in impaired immune responses between SDAT and aging.

Effects of substance P on the spontaneous binding of Salmonella minnesota R345 (Rb) to human peripheral blood lymphocytes

The effects of substance P (SP) on Salmonella minnesota R345 (Rb) binding to human peripheral blood lymphocytes (PBL) were evaluated. Two parameters of bacterial cytoadherence were considered, namely the binding lymphocytes (BL) and the number of bound-bacteria/lymphocyte (BB). The results showed that SP inhibits both BL and BB in a significant manner. Furthermore, distribution of Salmonella binding to CD4+ and CD8+ lymphocytes was studied following SP pretreatment of lymphoid cells. This neuropeptide is able to hamper the bacterial cytoadherence to both T-cell subpopulations and, in particular, the inhibitory effect on the T-suppressor/cytotoxic subset was more pronounced. These findings are discussed in terms of SP intervention in the mechanism of host protection against invading microorganisms.

Humoral and cellular immune responses to Salmonella typhi in patients with typhoid fever

Humoral and cellular immune responses to Salmonella typhi have been studied in nine children with typhoid fever. By using dot immunobinding assay, anti-O-polysaccharide chain and antilipid A antibody titers have been evaluated during the course of the disease. Anti-O-polysaccharide chain antibody titers are lower at the first week and increase up to the third week of the infection. On the other hand, antilipid A antibody levels, which are already higher at the beginning of the disease, progressively augment during the following weeks. Concerning cellular immunity to S. typhi, antibacterial activity mediated by typhoid peripheral mononuclear cells has been determined. Results show this function to be depressed in the initial phase of typhoid, increasing with the time. Together, these data bring new insight on immunity in typhoid patients.

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.

Depression of direct plaque-forming cell response in mouse spleen cell cultures by aggregated IgG2b-induced factors

Mouse spleen cells were treated with concanavalin A (Con A) or aggregated mouse IgG2b for 48 h in culture. When cells thus treated were added to fresh mouse spleen cell cultures immunized with SRBC they depressed the response of B lymphocytes as measured by enumerating plaque forming cells (PFC) on the fourth day of culture. When supernatant from cells cultured with IgG2b was added to immunized cultures this resulted in depression of PFC generation similar to that observed by addition of treated cells. The depression observed was essentially in the same range as that observed by addition of Con A treated cells or their supernatant. These observations extend previous work suggesting that IgG2b-induced PFC depression may result from activation of suppressor T cells with elaboration of soluble suppressor factors. This mechanism of immunomodulation may be important in the pathogenesis of immune complex disorders.

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.

Redistribution of mouse spleen cell Fc receptors following treatment with mouse or human aggregated immunoglobulin G

Mouse spleen cells treated with the Fc receptor ligands mouse IgG2b and human IgG, followed or not by a second antibody, exhibit different patterns of redistribution. In the work reported here we have examined the redistribution of Fc receptors (FcR) after binding of aggregated mouse IgG2b (Alg) or of Alg followed by anti-lg. We were particularly interested in learning whether binding of isologous Alg to FcR is followed by significant redistribution and shedding of Alg-FcR complexes. Mouse IgG2b alone will not induce capping even after 60 min at 37 degrees C. Human IgG induces some capping with minor shedding of complexes. Human IgG followed by anti-IgG readily induces capping by 15 min on 70% of the cells. This treatment also induces capping by 60 min at 20 degrees C on about 80% of the cells with a moderate degree of shedding of complexes. This is in agreement with the concept that the crosslinking required for FcR capping can be best induced with a second antibody. It is of interest, however, that heterologous IgG, unlike isologous, can induce a modest degree of capping and slight shedding even without the second antibody, suggesting that some crosslinking occurs with heterologous IgG.

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.

Cytochalasin A inhibits B-lymphocyte capping and activation by antigens

Cytochalasin B (CB) has been shown to be a potent depressant of the antigen-induced clone expansion and terminal differentiation of mouse B-lymphocytes to antibody-forming cells. This effect could be the result of the microfilament-disrupting effect of CB with subsequent inhibition of antigen-sIg complex redistribution, a series of events which seems to be necessary for B-lymphocyte activation. CB is not very active in depressing capping and will inhibit glucose transport. To further investigate the mechanism of action of cytochalasins, the effect of cytochalasin A (CA) on cap formation and plaque-forming cell generation was studied, since CA is less inhibitory of glucose transport and more inhibitory of cap formation. The results presented here indicate that complexes of anti-Ig-sIg will be prevented from capping by as little as 1 microgram of CA, a quantity sufficient to depress markedly the generation of plaque-forming cells to SRBC in culture. These results further confirm our conclusion that the depression of B-lymphocyte activation may be related to the depression of cap formation. It also strongly suggested that inhibition of glucose transport can be regraded as a negligible factor in this depression.

Lack of effect of exogenous prostaglandins on Fc receptor expression of mouse splenocytes

Previous work has shown that Prostaglandin E1 (PGE1) and other cyclic AMP elevating agents increase the expression of Fc receptors for IgG (FcR) on the murine pre-B cell lymphoma ABE-8 (Burchiel and Warner, 1980). We have investigated here the effect of Prostaglandins E1, E2, F1alpha, F2alpha on FcR expression of normal mouse lymphocytes. FcR were detected by an indirect fluorescent technique on B lymphocytes. The results show that Prostaglandins in culture did not induced any significant change of FcR + lymphocytes. The results are discussed in terms of the role of FcR in the ontogeny and functions of B lymphocytes.

Effect of prostaglandins on mouse erythrocyte rosette-forming human lymphocytes

Prostaglandins (PGs) E2 and F2 alpha, preincubated with human lymphocytes for short periods of time inhibit mouse erythrocyte rosette formation. The presence of calcium ions does not influence this effect, which is dose-dependent and relatively temperature-independent. These observations indicate the PG treatment of lymphocytes may be useful to distinguish a subclass of IgM-bearing mouse erythrocyte rosette-forming B lymphocytes, which is sensible to the modulating effect of Pgs.

Interaction between prostaglandins and human T lymphocytes: effect of PGE2 on E-receptor expression

E-rosette formation is not modified by preincubation of lymphocytes with prostaglandins (PGs) E1, F1 alpha, and F2 alpha. On the contrary, short preincubation with PGE2 affects active rosette-forming cells (Ea-RFC) and, only slightly, total RFC. This effect appears to be dose-dependent and relatively temperature-independent; it does not require calcium ions. Incubation with a fraction enriched in late RFC showed that PGE2 does not affect late rosette formation. It is postulated that PGE2 may redistribute surface receptors for sheep erythrocytes on T lymphocyte membranes. Thus, sensitivity to PGE2 may be considered another difference between early and late RFC.

[Behavior of natural immunity factors in systemic mycoses. I. Determination of lysozyme by means of a new technic]

Serum lysozyme of 138 patients with various systemic mycosis was determine by means of a new technique. It is reported that the levels of the enzyme are very low, particularly in the most serious diseases. The significance of this finding is discussed.

Effect of -3-thienylalanine on antibody synthesis. V. Immunosuppression in mice by short diet and drug treatments

The analogue of phenylalanine, beta-3-thienylalanine, depresses severely the primary and secondary immune response to sheep erythrocytes in mice when administered for a few days immediately before and after each injection of antigen. For this immunosuppression to occur, animals must be maintained on a phenylalanine-free diet during the times of drug injection since dietary phenylalanine will restore anamnestic response. With these experimental conditions, the number of direct and indirect plaque-forming cells is greatly reduced during immune responses. The finding that marked immunosuppression can be obtained with a very short drug and diet treatment points to a potential usefullness of the analogue as a powerful immunosuppressant.

Effect of β-3-Thienylalanine on Antibody Synthesis IV. Suppression of the Immune Response in Mice

The analogue of phenylalanine, β-3-thienylalanine (β-3-TA), inhibits the primary and secondary immune responses to sheep red blood cells in CBA mice fed with phenylalanine-free diet. The optimal dose of β-3-TA needed to obtain maximum immunosuppression with minimal toxicity is 250 mg per kg per day. The drug is maximally effective when administered for 7 days, beginning 2 days prior to primary immunization. With these experimental conditions, the antibody titers and the numbers of direct and indirect plaque-forming cells are greatly reduced during the primary and the secondary immune response.

Interaction between red cell stroma and streptolysin O: inhibition of cytotoxic activity

A blood red cell stroma extract neutralizes cytotoxic activity of streptolysin O. The component responsible for inhibition was precipitated by 60% ammonium sulfate and by lysozyme.