IMMUNOLOGICAL FACTORS AND RISK OF INFECTION IN PLATEAU-PHASE MYELOMA

Aims-A series of patients with myeloma were investigated to assess whe ther immunological risk factors predisposing to serious infection coul d be identified.Methods-Patients (n = 102) with predominantly plateau phase myeloma were monitored prospectively for infections. Immunologic al parameters including total non-paraprotein immunoglobulins and spec ific antibody titres were measured in all patients and compared with a control population of healthy individuals of a similar age; response to immunisation with Pneumovax II, tetanus and diphtheria toxoids and IgG subclasses were measured in a subgroup of 41 patients. Other chara cteristics investigated for any association with infection included ag e, sex, paraprotein type, disease stage, and chemotherapy. Results-Spe cific antibody titres to pneumococcal capsular polysaccharides and tet anus and diphtheria toxoids were significantly reduced compared with t he control population. Low antipneumococcal and anti Escherichia coli titres correlated with risk of serious infection and low antipneumococ cal titres with severity of non-paraprotein immunosuppression. In 41 i mmunised patients responses to Pneumovax II, tetanus and diphtheria to xoids were poor; IgG subclass levels were significantly reduced and a poor IgG response to Pneumovax II immunisation was associated with an increased risk of septicaemia and low IgG2 levels. The overall serious infection rate was 0.92 infections per patient year and was four time s higher during periods of active disease (1.90) compared with plateau phase myeloma (0.49). The predominant site of infection was the respi ratory tract. Clinical and laboratory parameters showed only male sex and reduced non-paraprotein IgG and IgA levels to be significantly ass ociated with at least one serious infection. Conclusions-A subgroup of patients with myeloma with poor IgG responses to exogenous antigens, who are at increased risk of serious infection, can be identified and may benefit from replacement immunoglobulin therapy to reduce the risk of infection.