[Age-related changes of B-cell immune function in patients with subacute myelo-optico-neuropathy (SMON)]

Several kinds of immunological abnormalities have been found more frequently in patients with subacute myelo-optico-neuropathy (SMON). To investigate whether the B-cell immune system is implicated in aging in patients with SMON, we examined serum levels of immunoglobulin including IgG, IgM, and IgA, and the number of CD20+ cells (B lymphocytes) and CD20+ CD23+ cells (activated B lymphocytes) using flow cytometry, and compared them with those in age-matched controls. We also investigated whether the number of HLA-DR+ cells was correlated with those of CD20+ cells, CD20+ CD23+ cells, or HLA-DR+CD3+ cells (activated T lymphocytes) in patients with SMON. Serum levels of IgG, IgM and IgA were decreased with aging both in the patients with SMON and in the controls, and no significant difference was found between the two groups. Although the patients with SMON tended to show higher levels of CD20+ and CD20+ CD23+ cells than the age-matched controls, there were no significant differences between the two groups. The number of HLA-DR+ cells was correlated not with that of CD20+ cells or CD20+ CD23+ cells, but with that of HLA-DR+CD3+ cells. In patients with SMON, it is likely that the B-cell immune system is mainly implicated in the effect of aging, but it is unlikely that other factors than aging are associated with the B-cell immune system. The increase in the number of HLA-DR+ cells associated with aging in patients with SMON reflects the increase in the number of activated T lymphocytes, and is not correlated with the changes of B lymphocytes.