On a mechanism of low level of Ig in a patient with multiple myeloma

Abstract

On the decrease in polyclonal Ig levels in patients with multiple myeloma (MM), several hypotheses have been proposed. By measuring in vitro Ig synthesis by mononuclear cells from peripheral blood (PMC) and from bone marrow aspirates (BMC) in a patient with IgG K myeloma, interesting results were obtained.The patient's WBC and lymphocytes are normal in number. Serum Ig levels were IgA 27, IgG 993 and IgM 58mg/dl. Urinary excretion of Bence-Jones protein was 7_??_10g/day. The amounts of IgG synthesized by PMC were markedly reduced, while those of IgA and IgM were almost equal to normal values. Hyperactivity of IgG specific suppressor T cells was responsible for the impairment of IgG synthesis. The amounts of Ig synthesis by BMC were markedly impaired for IgA and IgM and some what low for IgG. BMC could synthesize IgG without PWM-stimulation and moreover, B cells in BMC could synthesize IgG in the absence of T cells. Therefore, IgG synthesized by BMC was probably myeloma protein, not polyclonal IgG.Considering these results, we proposed a hypothesis that low levels of polyclonal IgA and IgM in this case were certainly caused by decreased synthesis of them in the bone marrow. Low level of IgG was caused by impaired synthesis of polyclonal IgG in PMC and also reduced synthesis of myeloma protein in the bone marrow. As myeloma protein synthesis by BMC was reduced, this case seems to belong to so called “oligo-M-component type” in multiple myeloma.