Altered immune function in relatives of schizophrenia patients

By Mark Cowen

Schizophrenia patients and their unaffected first-degree relatives exhibit immune system alterations compared with mentally healthy individuals, researchers report.

The team found that levels of four proinflammatory cytokines were significantly elevated in schizophrenia patients compared with controls, while levels of three proinflammatory cytokines were significantly elevated in their first-degree relatives.

Isabel Martínez-Gras (Complutense University, Madrid, Spain) and colleagues say that "the finding of abnormal cytokine levels both in schizophrenic patients and their first-degree unaffected relatives suggests that these immunological anomalies could be a possible endophenotype for this illness."

The researchers studied 36 men with chronic schizophrenia (mean illness duration 12 years), 18 of their unaffected first-degree male relatives (11 fathers and seven brothers), and 36 age-matched mentally healthy male controls.

Blood samples were collected from all of the participants and assessed for levels of the proinflammatory cytokines interleukin (IL)-1β, soluble IL-2 receptor (sIL-2R), IL-6, IL-12p70, tumor necrosis factor (TNF)-α, and interferon (IFN)-γ, as well as for levels of the anti-inflammatory cytokines IL-4 and IL-10, using enzyme-linked immunosorbent assays.

Analysis revealed that patients with schizophrenia had significantly higher serum levels of sIL-2R, IL-6, TNF-α, and IFN-γ, and significantly lower levels of IL-4 than controls.

The unaffected relatives of patients with schizophrenia also had significantly higher levels of sIL-2R, IL-6 and TNF-α than controls, but not as high as those in the schizophrenia patients.

Adjustment for differences in age, body mass index, smoking, and socioeconomic status among the groups did not affect the findings, the researchers note.

Martínez-Gras and team conclude in the journal Psychiatry Research: "Our results demonstrate the existence of alterations in the serum levels of cytokines both in schizophrenic patients and their first-degree relatives, therefore the cytokine levels could be a useful test for helping to stratify potential schizophrenia patients."

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