Natural killer T cells in families of patients with systemic lupus erythematosus: their possible role in regulation of IGG production.

Objective: To determine whether there is a link between the frequency of natural killer T (NKT) cells and high levels of IgG in patients with systemic lupus erythematosus (SLE) and their relatives.

Methods: Blood samples were obtained from patients with SLE, their first-degree relatives, patients with rheumatoid arthritis (RA), and healthy control subjects. The frequency of NKT cells (defined as CD56+ T cells) was expressed as a percentage of total blood lymphocytes.