All-trans retinoic acid potentiates the ability of interferon beta-1b to augment suppressor cell function in multiple sclerosis.

OBJECTIVE

To determine the effects of combination all-trans retinoic acid (RA) and interferon beta-1b therapy on immune system functions potentially relevant to multiple sclerosis (MS).

DESIGN

Interferon gamma-secreting cells, T suppressor cell function, and lymphocyte proliferative responses were assayed using peripheral blood mononuclear cells from patients with MS and control subjects under control conditions and in the presence of interferon beta-1b, RA, and the 2 combined.

SETTING

A university hospital MS clinic.

PARTICIPANTS

Seventeen patients with secondarily progressive MS and 25 control subjects.

RESULTS

Interferon beta-1b use increased interferon gamma-secreting cell counts, augmented T suppressor cell function, and inhibited T-cell proliferation. Therapy with RA decreased interferon gamma-secreting cell counts, had a minimal positive effect on T suppressor cell function, and had no effect on T-cell proliferation. When RA and interferon beta-1b were combined, the inhibitory effect of RA on interferon gamma-secreting cells predominated, T suppressor cell function increased synergistically over the increment observed with interferon beta-1b use alone, and the inhibitory effect of interferon beta-1b alone on T-cell proliferation remained unchanged.

CONCLUSIONS

Treatment with interferon beta-1b partially restores defective T suppressor cell function in patients with MS. This potentially beneficial action is synergistically potentiated by RA. Interferon beta-1b increases the number of interferon gamma-secreting cells in the circulation when treatment is initiated. A similar increment in interferon gamma-secreting cells is observed when interferon beta-1b is added to cultural peripheral blood mononuclear cells in vitro. This potentially deleterious action of interferon beta-1b is reversed by RA. Interferon beta-1b inhibits lymphocyte proliferation modestly but reproducibly. This action of interferon beta-1b is unaltered by RA. These data provide a rationale for a trial of combination treatment with interferon beta-1b and RA in patients with MS.