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Serum factors which suppress natural cytotoxicity in cancer patients
Abstract:
Spontaneous cytotoxicity mediated by natural killer (NK) cells is potentially an important mechanism of immunosurveillance against tumor or virus-infected cells. NK activity is impaired in many cancer patients. This study investigated the possibility that humoral factors are responsible for depressed NK activity in cancer patients and examined whether these factors were anti-lymphocyte antibodies (ALA) or immune complexes. The degree of NK suppression induced by 20 cancer patients' sera was determined by preincubating normal peripheral blood mononuclear cells with cancer sera. Eight of the 20 serum samples from cancer patients had NK-suppressive humoral factors. Elimination of immune aggregates by ultracentrifugation did not remove the inhibitory factors. The degree of NK suppression induced by cancer sera correlated with the extent of NK impairment in the serum donors (p less than 0.05). The cancer sera was examined for the presence of ALAs using flow cytometry. All cancer sera tested contained only low ALA reactivity to NK cell-enriched suspensions (less than 15%). This is in marked contrast to previous reports regarding NK-inhibitory systemic lupus erythematosus sera which contained large amounts of large granular lymphocyte (LGL) reactive ALAs. This study demonstrates that certain cancer sera suppress NK cell function. These inhibitory serum factors do not appear to be LGL-reactive ALAs or immune aggregates.
Insights
Certain cancer patient sera contain factors that suppress natural killer (NK) cell activity, a key part of the immune system. These factors are not anti-lymphocyte antibodies or immune complexes.
Area of Science:
- Immunology
- Cancer Research
- Cellular Biology
Background:
- Natural killer (NK) cell cytotoxicity is crucial for immunosurveillance against tumors and viral infections.
- Impaired NK cell activity is frequently observed in cancer patients, suggesting underlying inhibitory mechanisms.
- The role of humoral factors, such as anti-lymphocyte antibodies (ALA) or immune complexes, in this suppression is not fully understood.
Purpose of the Study:
- To investigate the presence and nature of humoral factors responsible for depressed NK cell activity in cancer patients.
- To determine if these suppressive factors are anti-lymphocyte antibodies (ALA) or immune complexes.
- To correlate NK cell suppression in vitro with NK cell impairment in cancer patients.
Main Methods:
- Incubation of normal peripheral blood mononuclear cells with sera from 20 cancer patients to assess NK cell suppression.
- Ultracentrifugation of cancer sera to remove immune aggregates and evaluate residual inhibitory effects.
- Flow cytometry analysis of cancer sera for the presence of anti-lymphocyte antibodies (ALA) reactive to NK cells.
Main Results:
- Eight out of 20 cancer patient serum samples exhibited NK cell-suppressive activity.
- Ultracentrifugation did not eliminate the NK-suppressive factors, indicating they are not immune aggregates.
- NK cell suppression induced by cancer sera correlated significantly with the degree of NK cell impairment in the patients (p < 0.05).
- Cancer sera showed minimal reactivity (<15%) with NK cell-enriched suspensions, suggesting the absence of significant LGL-reactive ALAs.
Conclusions:
- Specific cancer patient sera contain humoral factors that inhibit NK cell function.
- These inhibitory factors are distinct from LGL-reactive anti-lymphocyte antibodies and immune aggregates.
- The findings suggest a novel mechanism of NK cell suppression in cancer that warrants further investigation.