[Immunization of bagasse workers in Réunion]

We studied the immunological status of 45 bagasse workers from La Réunion to Thermoactinomyces sacchari. Twenty-six patients (58%) had a history of symptoms suggestive of sensitization to bagasse dusts; 19 (42%) were asymptomatic cases. Serum IgG was detected in 37 (80%) of the case patients and in 23 (88%) of the symptomatic cases. However, there was no significant difference in mean serum IgG titers of symptomatic (2.2 +/- 0.1) and asymptomatic cases (2.3 +/- 0.1). Analysis of isotypic specificity of IgG showed only IgG1 (71%) and/or IgG3 (60%) subclasses. Serum IgM and serum IgA were detected in only 7 (16%) and 2 (4%) of the case-patients, respectively. The detection of IgG was not found to correlate with either the case-patients' age, ethnicity, use of tobacco and alcohol, or their frequency, duration and amount of dust exposure. Therefore, the sensitization to T. sacchari antigens in bagasse dusts appears to be mainly mediated by IgG, subclasses 1 and 3, but is not pathogno monic of clinical symptomatology.