Tumour-related changes in natural killer cell activity in melanoma patients. Influence of stage of disease, tumour thickness and age of patients

The nexus of natural killer cells and melanoma tumor microenvironment: crosstalk, chemotherapeutic potential, and innovative NK cell-based therapeutic strategies

The metastasis of melanoma cells to regional lymph nodes and distant sites is an important contributor to cancer-related morbidity and mortality among patients with melanoma. This intricate process entails dynamic interactions involving tumor cells, cellular constituents, and non-cellular elements within the microenvironment. Moreover, both microenvironmental and systemic factors regulate the metastatic progression. Central to immunosurveillance for tumor cells are natural killer (NK) cells, prominent effectors of the innate immune system with potent antitumor and antimetastatic capabilities. Recognizing their pivotal role, contemporary immunotherapeutic strategies are actively integrating NK cells to combat metastatic tumors. Thus, a meticulous exploration of the interplay between metastatic melanoma and NK cells along the metastatic cascade is important. Given the critical involvement of NK cells within the melanoma tumor microenvironment, this comprehensive review illuminates the intricate relationship between components of the melanoma tumor microenvironment and NK cells, delineating their multifaceted roles. By shedding light on these critical aspects, this review advocates for a deeper understanding of NK cell dynamics within the melanoma context, driving forward transformative strategies to combat this cancer.

The immune-related role of beta-2-microglobulin in melanoma

Despite the remarkable success of immunotherapy in the treatment of melanoma, resistance to these agents still affects patient prognosis and response to therapies. Beta-2-microglobulin (β2M), an important subunit of major histocompatibility complex (MHC) class I, has important biological functions and roles in tumor immunity. In recent years, increasing studies have shown that B2M gene deficiency can inhibit MHC class I antigen presentation and lead to cancer immune evasion by affecting β2M expression. Based on this, B2M gene defect and T cell-based immunotherapy can interact to affect the efficacy of melanoma treatment. Taking into account the many recent advances in B2M-related melanoma immunity, here we discuss the immune function of the B2M gene in tumors, its common genetic alteration in melanoma, and its impact on and related improvements in melanoma immunotherapy. Our comprehensive review of β2M biology and its role in tumor immunotherapy contributes to understanding the potential of B2M gene as a promising melanoma therapeutic target.

Adoptive NK Cell Therapy: A Promising Treatment Prospect for Metastatic Melanoma

Simple Summary

The incidence of metastatic melanoma has been increasing over the past years with current therapies showing limited efficacy to cure the disease. Therefore, other options are being investigated, such as adoptive cell therapy (ACT) where activated immune cells are infused into a patient to attack melanoma. Natural killer (NK) cells are part of the innate immune system and extremely suitable for this kind of therapy since they show minimal toxicities in the clinical setting. In this review, we focus on current strategies for NK cell therapy and the development of new approaches that hold great promise for the treatment of advanced melanoma.

Abstract

Adoptive cell therapy (ACT) represents a promising alternative approach for patients with treatment-resistant metastatic melanoma. Lately, tumor infiltrating lymphocyte (TIL) therapy and chimeric antigen receptor (CAR)-T cell therapy have shown improved clinical outcome, compared to conventional chemotherapy or immunotherapy. Nevertheless, they are limited by immune escape of the tumor, cytokine release syndrome, and manufacturing challenges of autologous therapies. Conversely, the clinical use of Natural Killer (NK) cells has demonstrated a favorable clinical safety profile with minimal toxicities, providing an encouraging treatment alternative. Unlike T cells, NK cells are activated, amongst other mechanisms, by the downregulation of HLA class I molecules, thereby overcoming the hurdle of tumor immune escape. However, impairment of NK cell function has been observed in melanoma patients, resulting in deteriorated natural defense. To overcome this limitation, “activated” autologous or allogeneic NK cells have been infused into melanoma patients in early clinical trials, showing encouraging clinical benefit. Furthermore, as several NK cell-based therapeutics are being developed for different cancers, an emerging variety of approaches to increase migration and infiltration of adoptively transferred NK cells towards solid tumors is under preclinical investigation. These developments point to adoptive NK cell therapy as a highly promising treatment for metastatic melanoma in the future.

Targeting NK Cells to Enhance Melanoma Response to Immunotherapies

Natural killer (NK) cells are a key component of an innate immune system. They are important not only in initiating, but also in augmenting adaptive immune responses. NK cell activation is mediated by a carefully orchestrated balance between the signals from inhibitory and activating NK cell receptors. NK cells are potent producers of proinflammatory cytokines and are also able to elicit strong antitumor responses through secretion of perforin and granzyme B. Tumors can develop many mechanisms to evade NK cell antitumor responses, such as upregulating ligands for inhibitory receptors, secreting anti-inflammatory cytokines and recruiting immunosuppressive cells. Enhancing NK cell responses will likely augment the effectiveness of immunotherapies, and strategies to accomplish this are currently being evaluated in clinical trials. A comprehensive understanding of NK cell biology will likely provide additional opportunities to further leverage the antitumor effects of NK cells. In this review, we therefore sought to highlight NK cell biology, tumor evasion of NK cells and clinical trials that target NK cells.

Unique functional status of natural killer cells in metastatic stage IV melanoma patients and its modulation by chemotherapy

PURPOSE

Immunotherapy is an alternative for metastatic melanoma patients resistant to chemotherapy. Natural killer (NK) cells are powerful antileukemia effectors and their role in solid tumors is suspected. NK cell activation is regulated by a balance between activating receptors, which detect stress molecules on tumor cells, and HLA-I specific inhibitory receptors. Here, we studied the phenotype and function of NK cells in stage IV metastatic melanoma patients.

EXPERIMENTAL DESIGN

Circulating NK cells from 35 healthy donors and 51 patients were studied: 24 patients before chemotherapy (prechemotherapy), 17 patients 1 month after 1 to 4 lines of chemotherapy (postchemotherapy), and 10 patients analyzed pre- and postchemotherapy. NK functionality was carried out toward 2 primary metastatic melanoma cell lines, analyzed for the expression of NK receptor ligands.

RESULTS

NK cells from prechemotherapy patients exhibit an NKp46(dim)/NKG2A(dim) phenotype. In contrast, NK cells from postchemotherapy patients display high expression of NKp46 and NKG2A receptors. Purified NK cells from patients are efficiently activated in response to melanoma cells. Melanoma cells express different level of NKG2D ligands and HLA-I molecules. In agreements with their phenotype, NK cells from pre- and postchemotherapy patients present distinct functional status toward these primary melanoma cells. A dynamic label free assay was used to determine the pathways involved in the lysis of melanoma cells by IL-2-activated NK cells. NKG2D, NCR (natural cytotoxicity receptor), and DNAM-1 are involved in the NK-mediated lysis of melanoma cells.

CONCLUSIONS

These results provide new arguments and clues to design NK cell-based immunotherapeutic strategies for melanoma patients.

Immunomodulatory function of murine nk cell activity by alginate

The in vivo immunomodulatory function of the activity of murine natural killer (NK) cells induced by high mannuronic acid-containing alginate (HMA) was examined. HMA was injected i.p at doses of 25 and 100 mg/kg. The NK activity was 3 times higher with 100 mg/kg HMA than the baseline. In addition, in vitro studies of splenocytes cultured with HMA for 20 h showed a significant increase in NK activity at E:T ratio of 100:1; a 160% and 210% increase at 10 and 100 microg/mL, respectively. There was a six fold increase in interferon-gamma production in a postculture of splenocytes with 100 microg/mL HMA. HMA had no suppressive effects on the lymphocyte function in the presence or absence of mitogens. This suggests that HMA is useful in cancer immunotherapy.

Malignant melanoma in an HIV-infected man: a case report and literature review

Although it is not proven by causative association, several studies indicate that patients with acquired immune deficiency syndrome (AIDS) have a high risk for developing cutaneous malignancies, especially lymphoma and Kaposi's sarcoma. Other malignant cutaneous lesions seen in this patient population include basal-cell carcinoma, squamous-cell cancer, Bowen's disease, and rarely, malignant melanoma. We review the clinical course of a human immunodeficiency virus (HIV)-infected man with a superficial spreading melanoma of the scapula treated with wide local excision. Ten years later, he was diagnosed as having metastatic and widespread disease. By placing our patient's experience in context with other case reports, we sought to determine whether malignant melanoma in the HIV-infected population presents atypically or has a more aggressive natural history. The appearance of malignant melanoma in homosexual men may be coincidental or reflective of the expanding spectrum of HIV-associated diseases. Of the 22 patients reported to have malignant melanoma and HIV, approximately one-third had metastatic disease at the time of initial examination, and those with a decreased CD4+ cell count were most likely to have systemic symptoms. Melanomas among patients with HIV infection were often atypical in appearance, being multiple or metastatic, as is the case in other well-defined immunosuppressed groups. Further epidemiological and clinical studies are required to determine whether melanoma occurs more frequently or is more likely to metastasize in persons with HIV disease. Laboratory investigators must also concentrate on those factors in the setting of HIV disease that may contribute to melanocyte activation. Our patient's fulminant clinical course should alert clinicians to carefully evaluate patients with HIV infection and unusual pigmented cutaneous lesions, or who have a prior history of malignant melanoma.

Natural killer activity and serum immunosuppressive acidic protein levels in esophageal and gastric cancers

The natural killer (NK) activity of peripheral blood mononuclear cells and serum immunosuppressive acidic protein (IAP) levels were examined in patients with esophageal or gastric cancer, before and after surgery. Patients with stage IV esophageal or stage IV gastric cancer had significantly lower NK activity (39.5 +/- 14.8% and 37 +/- 11.6%, respectively), and also higher serum IAP levels (778 +/- 264 micrograms/mL and 633 +/- 156 micrograms/mL, respectively), than the corresponding control values (50 +/- 5.6% and 375 +/- 26 micrograms/mL, respectively). Patients with esophageal or gastric cancer who underwent curative resection had high NK activity (54.8 +/- 11.6% and 54.8 +/- 8.0%, respectively), and low IAP levels (471 +/- 116 micrograms/mL and 490 +/- 42 micrograms/mL, respectively), compared with those who underwent non-curative resection. Patients who underwent non-curative resection had lower NK activity and higher serum IAP levels than those who underwent curative resection, even 1 month after surgery. Mononuclear cells in the regional lymph nodes and tumor specimens showed significantly lower NK activity than those in the peripheral blood and spleen. Thus, NK activity and the IAP level reflected the immunocompetence, clinical course, and surgical curability of those patients. NK cells appeared not to have any significant antitumor activity in the regional lymph nodes or in the tumor itself, although they were still active in the peripheral blood.

Defective interferon-augmented natural killer cell activity in patients with metastatic malignant melanoma

Unstimulated and interferon (IFN)-stimulated natural killer cell (NK) activity was investigated in patients with malignant melanoma prior to the removal of the primary melanoma (stage I disease) or in patients with melanoma metastases. Unstimulated as well as IFN-stimulated NK activities, directed against the primarily NK-sensitive K562 cell line, were found not to differ significantly from the NK activity of healthy control subjects. In contrast, IFN-stimulated NK activity directed against the primarily NK-insensitive Chang hepatoma and JY cell lines was significantly lower in patients with metastatic melanoma than in patients with non-metastatic disease (Chang hepatoma cell line: P less than 0.02; JY cell line: P less than 0.0017) and - in experiments using the JY cell line - than in healthy controls (P less than 0.01). Stage I melanoma patients did not differ in their IFN-induced NK activity from healthy control subjects using Chang hepatoma and JY cell lines. Finally, the IFN-induced increase in NK activity directed against primarily NK-insensitive target cell lines was significant in stage I melanoma patients and in healthy controls (P less than 0.01, respectively), but not in patients with metastatic melanoma (P greater than 0.5). We thus conclude that patients with metastatic malignant melanoma exhibited a defect in IFN-augmented NK activity directed against primarily NK-insensitive targets.

Peripheral blood lymphocytes from thermal injury patients are defective in their ability to generate lymphokine-activated killer (LAK) cell activity

We have previously shown that natural killer (NK) cell activity against K562 tumor cells is severely depressed in thermal injury patients. In this study we have investigated whether the low NK cell activity present in peripheral blood lymphocytes (PBL) from thermal injury patients could be enhanced by in vitro culture with interleukin 2 (IL2) and whether PBL obtained from these patients could generate lymphokine-activated killer (LAK) cell activity against NK insensitive tumor targets. NK cell activity in PBL obtained from 12 different patients was greatly enhanced against K562 tumor cells after in vitro culture with IL2 for 3 days. In contrast, PBL obtained from these patients and incubated with IL2 had little to no cytotoxic activity when measured against a number of NK-insensitive tumor targets. The failure of PBL obtained from thermal injury patients to generate LAK cell activity was observed regardless of the culture time or the amount of IL2 added to the cultures. PBL from thermal injury patients demonstrated reduced proliferative responses to IL2 and, more importantly, contained suppressor cells which could inhibit the generation of LAK cell activity of normal PBL obtained from control individuals. These results clearly show that in some thermal injury patients NK cell activity can be enhanced by IL2 but these patients are defective in their ability to generate LAK cell activity.

Natural killer activity of peripheral blood lymphocytes and its relation to histopathological factors of lung cancer

This investigation was intended to determine whether the natural killer (NK) activity of peripheral blood lymphocytes (PBL) correlated with the histopathological factor, which is thought to be a result of a balance between tumor aggression and host resistance. The NK activity of PBL from 60 patients with lung cancer was measured by the lysis of 51Cr-labelled K562 target cells. The activity was significantly decreased with advancing stages of the disease, and inversely correlated with increased immunosuppressive substance levels of the serum. Histopathological factors, such as low grade pleural invasion of the tumor and abundant lymphoid cell infiltration around the tumor, were significantly associated with the high NK activity of PBL. These results show that a decrease in NK activity may play a role in identifying those individuals with a greater risk of cancer development.

NK cell density in malignant skin tumours--a stereological study

We determined the density of natural killer (NK) cells in frozen sections of malignant melanoma (nine cases), squamous cell carcinoma (six cases) and non-neoplastic tonsil (five cases) by immunohistological and stereological methods. The mean density of NK cells in malignant melanoma (5.0 +/- 1.5 X 10(3)/mm3) and in squamous cell carcinoma (5.1 +/- 2.7 X 10(3)/mm3) was significantly lower than in germinal centres of normal human tonsils (5.0 +/- 0.8 X 10(4)/mm3). The NK cell/tumour cell ratio (0.03 +/- 0.015 in malignant melanoma and 0.02 +/- 0.015 in squamous cell carcinoma) is 10(2)-10(4) times lower than that commonly used for in vitro assays. The possible role of NK cells in malignant skin tumours should be viewed with caution.

Phase II study of vaccinia melanoma cell lysates (VMCL) as adjuvant to surgical treatment of stage II melanoma. II. Effects on cell mediated cytotoxicity and leucocyte dependent antibody activity: immunological effects of VMCL in melanoma patients

Patients with stage II melanoma were vaccinated with vaccinia virus-induced melanoma cell lysates (VMCL). The vaccine contained viable vaccinia virus, membranous fragments and no intact nuclei. A number of antigens defined by monoclonal antibodies were detected in the vaccine including the ganglioside GD3 and DR antigens. Administration of the vaccine was associated with depression of natural killer cell activity against melanoma and K562 target cells in the first 3-6 months of treatment. Leucocyte dependent antibody (LDA) activity against melanoma cells was induced or increased in titre in approximately half of the patients studied. Continued vaccination was associated in a number of patients with a decrease in LDA titres. Studies on a small sample of patients revealed that this was associated with the development of serum factors which inhibited LDA activity. LDA activity appeared directed to non-MHC antigens on melanoma cells which were of at least two specificities. One specificity which was shared with antigens on a number of non-melanoma carcinoma cells was removed by absorption on fetal brain and may be similar to oncofetal antigens described by other workers. Reactivity against melanocytes was induced in some patients and may underline the development of vitiligo in several patients. These results suggest that vaccines prepared from VMCL may be a favourable method for increasing immune responses against melanoma.

Abnormal natural killer cytotoxicity in primary biliary cirrhosis: evidence for a functional deficiency of cytolytic effector cells

The in vitro cytotoxic activity of peripheral blood lymphocytes from patients with primary biliary cirrhosis was investigated to determine the mechanism of deficient spontaneous cell-mediated cytotoxicity in this disease. Using 51Cr-labeled Chang or K562 target cells, it was found that patients' lymphocytes mediated less natural killer cytotoxicity than lymphocytes from normal controls. Antibody-dependent cytotoxicity was normal in primary biliary cirrhosis. The natural killer activity of normal lymphocytes was inhibited neither by serum nor by lymphocytes from patients with primary biliary cirrhosis. The percentage of lymphocytes from patients that bound to target cells was normal. Furthermore, the percentages of lymphocytes that reacted with the monoclonal antibodies anti-Leu-7 and anti-Leu-11 were normal in patients. The percentage of lymphocytes that reacted with both anti-Leu-2 and anti-Leu-7, a subpopulation of cells that has low natural killer activity, was also normal in primary biliary cirrhosis. Interferon and interleukin-2 both augmented cytotoxic function of lymphocytes from primary biliary cirrhosis patients, however, the levels of cytotoxicity induced by these agents were less than corresponding levels exhibited by normal lymphocytes when similarly stimulated. These findings indicate that patients with primary biliary cirrhosis have diminished natural killer activity due to a functional defect of cytolytic effector cells.

Effects of recombinant leukocyte interferon (rIFN-alpha A) on tumour growth and immune responses in patients with metastatic melanoma

Studies were initiated to assess the response of patients with disseminated melanoma to recombinant alpha interferon (rIFN-alpha A) and to monitor effects of rIFN-alpha A on several tests of immune function. Twenty patients were treated with rIFN-alpha A given by i.m. injection in escalating doses from 15 to 50 X 10(6) um-2. The responses of two patients were considered unevaluable. Of the remainder there was complete remission of tumour in two and stable disease in two. Subsequent progression of tumour in one of the latter patients coincided with development of antibodies to IFN. Side effects (usually fatigue) were dose rate limiting in 11 patients. Laboratory tests on samples taken 6 hours after rIFN-alpha A indicated a marked lymphopenia and a reduction in natural killer (NK) cell activity particularly against K562 target cells. Longer term changes measured in samples taken 2 days after the previous rIFN-alpha A injections consisted of neutropenia and an increase in the T4/T8 ratio due mainly to a relative increase in OKT4 positive T cells compared to OKT8 positive T cells. NK activity against the K562 target cell increased in most patients during the first week of treatment and then returned to below or near pretreatment levels thereafter against the K562 target cell. This contrasted with NK activity against the melanoma target cell which showed a more gradual increase over the duration of the treatment in 6 patients. The latter correlated with an increase in mitogen stimulated IL 2 production from their blood lymphocytes and may indicate that the cytotoxic activity resulted from lymphokine-activated killer (LAK) cells. These results confirm the activity of rIFN-alpha A against melanoma in certain patients. They suggest that further studies are needed to select patients who may respond to rIFN-alpha A and to optimize treatment regimens. Tests of IL 2 production and LAK activity may assisted in achieving these objectives.

Impaired release of a soluble natural killer cytotoxic factor in systemic lupus erythematosus

Disease states characterized by abnormalities in immune regulation often demonstrate concomitant abnormalities in cytotoxicity mediated by natural killer (NK) cells. For example, some patients with systemic lupus erythematosus (SLE) have depressed NK activity despite the presence of normal numbers of effector cell:target cell conjugates. This study was designed to determine if defects in NK cell function were directly related to impaired release of a soluble cytotoxic factor. NK activity of peripheral blood mononuclear cells and large granular lymphocytes was measured using 51Cr-labeled K562 target cells in 4-hour release assays. The SLE patients had significantly decreased NK activity relative to normal controls. However, the number of effector cell:target cell conjugates was not different in SLE patients versus control subjects. The release of a soluble natural killer cytotoxic factor (NKCF) by peripheral blood mononuclear cells was measured by cytotoxicity induced in K562 cells. NKCF was released preferentially by suspensions enriched in NK cells (large granular lymphocytes). At a 1:1 dilution, NKCF release was significantly lower in SLE patients than in controls. The release of NKCF correlated well with NK activity. Thus, this study shows that the defect in NK cell activity in SLE patients may be related to an impairment in release of a soluble cytotoxic factor with specificity for NK cell-sensitive targets.

Current status and future prospects for adjuvant therapy of melanoma

Advances in the treatment of melanoma have resulted mainly from improved surgical management of the primary tumour assisted by a greater appreciation of major prognostic factors in the natural history of the disease. Further improvement in the treatment of melanoma will depend largely on introduction of methods to prevent recurrence of the disease. The present review discusses criteria for selection of patients with a high risk of recurrent disease and the adjuvant treatment that has been used in past studies to prevent recurrences. With few exceptions various regimens of chemotherapy, non-specific immunotherapy with bacterial products or combinations of these treatments have not increased disease free or survival periods. Immunotherapy with various sources of melanoma antigens or with viral lysates of melanoma cells have produced encouraging results in uncontrolled studies and require further evaluation. Several advances appear to provide scope for new initiatives in immunotherapy. These include an appreciation of the role of suppressor cells in regulation of immune responses against tumour cells and possible methods to inhibit their activity. A second is the definition of various lymphokines involved in generation of immune responses (particularly interleukin 2) and development of in vitro methods for large scale production of these factors. Thirdly, methods are becoming available to define the heterogeneity of tumour cells in terms of cell surface antigens or their release of soluble factors which may help select treatments appropriate to each patient.

Natural killer cell defects resulting from thermal injury

Peripheral blood mononuclear lymphocytes (PBL) from thermal injury patients were examined for their ability to mediate spontaneous (NK) cytotoxic activity against K562 tumor cells. NK cell numbers were quantitated in burn patients using the fluorescein isothiocyanate-conjugated monoclonal antibody Leu-7 and an Ortho cell sorter. NK activity of burn patients was only 30% of control levels. Thus, at a 50:1 effector:target cell ratio, burn patients' PBL gave a mean of 18% killing as compared to 60% killing mediated by control PBL (14 individuals). Pretreatment of PBL with interferon-gamma or interferon-alpha enhanced NK activity of normal PBL but had no effect on the NK activity of PBL from burn patients. The number of cells bearing antigen recognized by Leu-7 was variable in burn patients, with some patients having decreased (less than 5%), normal (8-10%), or elevated (20-40%) numbers of Leu-7 bearing PBL. No differences were observed in the total numbers of PBL in burn patients when compared to control individuals. These results indicate that NK activity does not correlate with the percentage of Leu-7 bearing cells present in PBL and that the inability of thermal injury patients to mediate normal NK function may contribute to their susceptibilities to viral infections.

Interferon-alpha regulation of lymphocyte function in systemic lupus erythematosus

Interferon (IFN) production and responsiveness are abnormal in some patients with systemic lupus erythematosus (SLE). The present investigation was designed to further delineate these abnormalities of IFN response. The response to IFN-alpha was determined in peripheral blood mononuclear cells (PBMC) using the natural killer (NK) cell assay, the concanavalin A (Con A)-induced T-cell proliferation assay, and the pokeweed mitogen (PWM) blastogensis system. The average NK cell activity was impaired in SLE patients (19.7 +/- 3.8 LU/10(7) cells; n = 22) compared to 24 normal controls (45.6 +/- 7.2 LU/10(7) cells; n = 24) (P less than 0.05). In addition, the response to IFN in the NK cell system was impaired in SLE (110.0 +/- 38.0% enhancement) compared to controls (320.0 +/- 94.0% enhancement; +/- SD P less than 0.05). In contrast to the impaired IFN response of the NK cell in SLE, the effect of IFN on Con A- and PWM-induced blastogenesis in SLE was normal (P greater than 0.1). Thus, the defect in IFN response in SLE appeared to be confined to the NK cell system, but was not present in the other assay systems. To determine if the impaired IFN response might be secondary to impaired release of natural killer cytotoxic factor (NKCF) induced by IFN, NKCF was generated from PBMC in the presence of IFN. IFN-induced NKCF release was markedly impaired in SLE (8.9 +/- 11.7%) relative to normal controls (22.3 +/- 11.2%) (P less than 0.05). IFN-induced release of NKCF in SLE also closely correlated with IFN-induced NK enhancement (r = .83, P less than 0.05). No depletion of NK cells was noted using the monoclonal antibody HNK-1. Thus, this study demonstrates for the first time that the insensitivity to IFN in SLE is not a universal lymphocyte defect but appears to be isolated to the NK cell which is functionally abnormal.

Acting mechanisms of Lentinan in human--II. Enhancement of non-specific cell-mediated cytotoxicity as an interferon inducer

The immunopotentiator "Lentinan" augmented the cell-mediated cytotoxicity in humans. (a) The activation of killer T cells by the mixed lymphocyte culture was accelerated only when responder cells were mixed with both a suboptimum number of stimulator cells and Lentinan. (b) The interferon level in the peripheral blood circulation of cancer patients was elevated in 12 h following Lentinan administration, and natural killer activity of peripheral mononuclear cells was enhanced in 48 h. These data indicate that Lentinan favorably affects the host mechanisms of man.

A modified short-term cytotoxicity test: assessment of natural cell-mediated cytotoxicity in whole blood

Using whole blood from normal subjects, we have observed natural killing of K562 cells in a 4 h 51Cr-release assay comparable with that shown by separated PBMC and whole blood depleted of serum components. Separated plasma was not toxic towards K562 targets, and failed to potentiate the level of PBMC cytotoxicity through ADCC. The presence of red blood cells did not influence natural killing. The natural cytotoxicity of whole blood was augmented by interferon and depressed by prostaglandins E1 and E2. Studies with appropriate control blood fractions show that cytotoxicity tests with whole blood provide results reflecting natural cell-mediated cytotoxicity.

Natural killer cell in systemic lupus erythematosus. Defects in effector lytic activity and response to interferon and interferon inducers

Spontaneous cytotoxicity mediated by natural killer (NK) cells is impaired in several human diseases including systemic lupus erythematosus (SLE). The precise mechanism(s) by which NK activity is suppressed in patients with SLE is generally unknown. The present study was designed to focus on cellular defects per se in NK cells from patients with SLE. It was observed that the usual enhancing effect of interferon (IF) and IF inducers was markedly impaired in SLE patients. Of 24 SLE patients studied, 17 had significantly decreased NK activity relative to controls. NK activity had a significant negative correlation with clinical activity score (r = -0.56, P less than 0.005) but was not correlated with corticosteroid dose, antinuclear antibody titers, total hemolytic complement (CH50), or sedimentation rate. Furthermore, significant depressions in NK activity correlated with variations in disease activity in six patients followed serially. Depressed NK function could not be reversed by prolonged in vitro incubation at 37 degrees C or with protease treatment. Furthermore, depressed NK activity was not altered by removal of glass adherent cells nor was a suppression of NK activity in normal controls seen by the addition of SLE peripheral mononuclear cells. No reversal of depressed activity to normal levels was seen by the addition of indomethacin nor did the supernatants from SLE cell cultures cause a suppression of normal NK function. NK activity in SLE patients did not respond normally to IF inducers (poly-I:C and concanavalin A) even if the SLE patients had normal NK function. The response of SLE cells to exogenous IF was also impaired. The number of effector-target conjugates was quantitated with several target cells (K562, Yac-1, Fravel) in SLE patients and controls. A significant correlation between the proportion of glass nonadherent mononuclear cells that formed effector-target conjugates with these various targets and the magnitude of NK lysis was observed. However, SLE and normal subjects had equal numbers of effector-target conjugates independent of NK function. Release of a soluble cytotoxic factor was induced with concanavalin A, and was markedly impaired in SLE patients relative to normal controls. Thus, impaired NK cell function in SLE does not appear to be related to cell-mediated suppressive mechanisms or to the deletion of effector cells; rather, the decreased NK activity may be related to an impaired release of a soluble cytotoxic factor.

Immunological effects of solarium exposure

Normal volunteers underwent a standard course of treatment to acquire a suntan in a commercial solarium, and tests of immune function were carried out before, on completion, and 2 weeks after completion of radiation exposure. Compared with age and sex matched concurrent controls, the test subjects had reduced skin test responses to dinitrochlorobenzene (DNCB), slightly reduced blood lymphocyte numbers, and changes in the proportion of lymphocyte subpopulations. This included a relative increase in total (OKT3+) T-cell numbers which was attributable to an increase in the OKT8+ suppressor/cytotoxic subset of T cells. OKT4+ helper T cells were reduced and there was a significant decrease in the OKT4/OKT8 ratio. Other changes included a significant increase in suppressor T-cell activity against IgG production in vitro and depression of natural killer cell activity. These changes were still present in some subjects 2 weeks after solarium exposure.

The effect of surgery and chemotherapy on blood NK cell activity in patients with ovarian cancer

The cytotoxic activity of NK cells in peripheral blood was studied in 15 patients with ovarian cancer Stage III and IV before and after surgery and ten-week intramuscular therapy with thiotepa. An evident decrease in NK activity was found 24 hours after surgery, with a slow return toward normal values within 7-9 days. No differences between patients with explorative laparotomy and with extirpation of the tumor were observed. The mechanism of the decreased NK cytotoxicity remains unknown but there was a concomitant reduction in the number of blood mononuclears. A second drop in NK activity occurred after chemotherapy. It was most likely due to the drug bone marrow depression. No evident correlation between the reduced NK activity and advancement of the disease could be found.

Natural killer cells in human solid tumors

Natural killer (NK) cells have been studied in human neoplastic diseases in an effort to assess the role of these cells in the control of human neoplasia and to monitor the effects of therapeutic regimens expected to affect this reactivity. NK activity measured against susceptible cell lines is usually somewhat depressed in patients bearing advanced solid tumors, but not at early disease stages. Lymphoid cells associated with solid tumor tissues or effusions have usually low NK cytotoxicity, with considerable differences among histologic types (e.g., nasopharyngeal carcinoma versus other tumors) or at different sites involved by the same tumor (e.g., peritoneal effusions versus solid lesions in ovarian carcinoma). The low levels of NK activity of tumor-associated lymphoid cells are primarily related to a low frequency in the relevant effector cells at the tumor site, although suppression of the in vitro maintenance of cytotoxicity by in situ macrophages and lymphocytes has been described in a few patients. Treatment with immunopharmacologic agents, interferons in particular, has been reported to augment NK activity in cancer patients, but it is unclear how blood NK activity relates to tissue levels of this reactivity. Limited evidence indicates that blood NK levels need not be representative of the activity of tumor associated lymphoid cells. Most studies on NK cells in human neoplasia have dealt with reactivity against susceptible tissue culture lines, but freshly isolated human tumors are generally relatively resistant to these effector cells, particularly when autologous lymphoid cells are used. The resistance of fresh human neoplastic cells to NK activity has not been studied extensively and, together with the poor localization at the tumor site of NK effectors, it represents a major difficulty in envisaging a role for these cells in the control of established human neoplasia.

Immune responses of DBA/2 mice bearing melanoma tumors: cell-mediated immune responses after challenge with vaccinia virus

Cell-mediated immune responses in DBA/2 mice bearing melanoma tumors (TB-mice) were measured and compared to similar responses in mice without tumors (C-mice). Splenic lymphocytes from TB-mice had a reduced capacity to respond to both B and T-cell mitogens, but TB-mice responded to infection with vaccinia virus by developing a virus-specific cytotoxic T-cell response equal to that measured with splenic effectors prepared from virus-infected C-mice. NK-cell activity, as measured by the in vitro lysis of YAC-1 targets by splenic effectors, was significantly depressed in TB-mice but, after infection of the animals with vaccinia virus, was restored to levels equal to that measured with splenic effectors prepared from C-mice. Doses of vaccinia virus, strain WR which elicited vaccinia-virus-specific cytotoxic T cells or stimulated NK-cell activity, failed to elicit or stimulate cytotoxic effectors specific for S91-melanoma tumor cells.

Natural killer cell activity and response to phytohaemagglutinin compared with the histological diagnosis of patients with transitional cell carcinoma of the bladder

In vitro tests of immune reactivity in patients with transitional cell carcinoma (TCC) of the urinary bladder were compared with the clinical and histological diagnosis. Response of peripheral blood lymphocytes to the mitogen phytohaemagglutinin (PHA) tended to be reduced in patients with more advanced disease, although the difference between patients with advanced disease and those with early disease or controls was not statistically significant (P greater than 0.05). Assessment of natural killer (NK) cell activity in the same patients showed no change in levels of reactivity at any stage of the disease. There was no difference between the NK cell activity of patients with TCC of the bladder and normal controls.

Induction of cytotoxic activity in human lymphocytes against autologous and allogeneic melanoma cells in vitro by culture with interleukin 2

The influence of interleukin 2(IL2) on the cytotoxic activity of lymphocytes from patients with melanoma against autologous and a variety of allogeneic melanoma cells was studied. IL2 was produced from blood lymphocytes cultured for 24 h with phytohaemagglutinin (PHA) and purified by membrane chromatography to exclude PHA. Lymphocytes from 13 patients with melanoma at various clinical stages were cultured fro 6 days with IL2 (2 U/ml) and then tested for cytotoxic activity against autologous melanoma cells, three allogeneic melanoma and three non-melanoma cells. Autologous cytotoxicity was generated by culture with IL2 alone and was not increased by culture with both IL2 and autologous tumour cells. Marked increases in cytotoxic activity were also generated against the allogeneic target cells and were maximal against the NK-insensitive Chang target cells. Similar degrees of cytotoxicity were induced by IL2 stimulation of lymphocytes from melanoma patients, patients with nonmelanoma carcinoma and normal subjects against the allogeneic target cells. Cold target inhibition studies were carried out against IL2 induced autologous cytotoxicity in five patients. In four of five studies the autologous target cells inhibited more than the allogeneic target cells. There was no significant difference between the inhibition produced by allogeneic melanoma cells and that produced by non-melanoma cells. Similarly, in studies against allogeneic target cells, there was no significant difference in the inhibition produced by allogeneic melanoma compared to non-melanoma target cells. This applied irrespective of whether effector cells were from melanoma or non-melanoma subjects. These results suggest that lymphocytes from patients with melanoma are primed against autologous antigens in vivo and that provision of a second signal, IL2, in vitro can induce cytotoxicity against the autologous tumour. The cytotoxicity generated against the allogeneic target cells did not appear to have specificity to melanoma. Several results, such as the pattern of cytotoxicity against the target cells and change in cell surface markers on the lymphocytes during culture, suggested that cytotoxicity was mediated by activated T cells rather than by nature killer cells. These findings appear to have important implications both in the understanding of tumor host relationships and for the use of IL2 in therapy.

Suppressor cell activity in melanoma patients. I. Relation to tumor growth an immunoglobulin levels in vivo

The effect of tumor growth on the suppressor cell activity of melanoma patients was examined by measurement of immunoglobulin produced in vitro in pokeweed mitogen (PWM)-stimulated cultures of B and T lymphocytes. B and T cells were separated by sheep red blood cell rosetting and suppressor cell activity was assessed by comparison of immunoglobulins produced in cultures with irradiated T cells (2,000 rads) to that with unirradiated T cells. In the majority of patients with localized melanoma, radiosensitive suppressor T cells were detected and appeared to be an augmentation of a normal physiological state. In patients with Stage I and II melanoma, removal of the tumor resulted in a significant decrease in suppressor activity against IgA and IgM but not against IgG production. Similar sequential changes in suppressor cell activity against IgA and IgM but not against IgG production. Similar sequential changes in suppressor cell activity were not generally detected in patients who had surgery for skin graft after previous removal of the primary melanoma or in patients undergoing surgery for non-malignant conditions. Sequential studies on the levels of serum immunoglobulins showed an apparent trend for immunoglobulins to increase after surgery. Of particular importance, the decrease in in vitro suppressor cell activity against IgM and IgG production after tumor removal in individual patients was significantly associated with an increase in immunoglobulin levels in the serum of these patients. It is suggested that these findings may account in part for the absence of detectable antibody responses to melanoma antigens in many patients and for the generalized immunodeficiency in patients with disseminated melanoma.