Distribution of IgG subclasses in antimonial unresponsive Indian kala-azarpatients

Sodium antimony gluconate (SAG) is the mainstay of treatment for visceral l eishmaniasis (VL) or kala-azar. In view of the increasing incidence of refr actoriness to SAG in India, we compared the levels of parasite-specific IgG and IgG subclasses in 20 longitudinally followed up kala-azar patients. In both SAG-responsive (n = 10) and unresponsive patients (n = 10), the level s of total IgG, IgG1, IgG2, IgG3 and IgG4 were increased, the rank order be ing IgG1 > IgG2 > IgG3 = IgG4. Following treatment, a significant decrease in total IgG and the four subclasses occurred in the SAG-responsive group, whereas in the SAG-unresponsive group these levels were unchanged or slight ly increased. Therefore, monitoring of IgG1 and IgG2 levels in Indian kala- azar patients is a good serologic alternative to monitoring the disease sta tus.