The effect of uraemic "middle-sized molecules" on T lymphocyte functions.

The activity of the leucocyte inhibitory factor (LIF) stimulated with Concanavalin A was examined in chronic uraemic, haemodialysed patients. It was found that the LIF activity decreased in chronic uraemic patients as compared with the normal controls. The absolute T lymphocyte count and active E rosette formation also decreased. In in vitro experiments the authors have also examined the inhibitory effect of the so-called "middle-sized molecule" (MSM) on uraemic materials separated from the serum and the haemofiltrate. They observed that the materials with a molecular weight of 1000-1500 isolated both from the serum and the haemofiltrate significantly inhibited the Con A stimulated LIF production of normal lymphocytes and decreased the ratio of the active E rosette-forming T lymphocytes. On the basis of their experiments the MSM uraemic materials are considered responsible for the decreased immune reactivity of uraemic patients. These uraemic toxins can be dialysed.