Ra. Lawrence et al., ADULT AND MICROFILARIAL STAGES OF THE FILARIAL PARASITE BRUGIA-MALAYISTIMULATE CONTRASTING CYTOKINE AND IG ISOTYPE RESPONSES IN BALB C MICE/, The Journal of immunology, 153(3), 1994, pp. 1216-1224
Natural infection with filarial nematode parasites shows many characte
ristics of a Th2 immune response. In these infections, long-lived adul
t worms inhabit the lymphatics, releasing larval microfilariae (Mf) in
to the blood stream. To compare the effect of these different developm
ental stages on the mammalian immune system, Mf and adult worms of eit
her sex were implanted into BALB/c mice, in which they survive for at
least 28 days. Serum Ab responses showed that whereas Mf stimulated sp
ecific Abs of all IgG subclasses, but little total IgE, adult worms st
imulated only IgG1 and IgE responses. Splenocytes from implanted mice
were stimulated in vitro with specific Ag or Con A and assayed for pro
liferation and profiles of cytokine secretion. Cells from Mf-infected
mice secreted high levels of IFN-gamma (30 U/ml) throughout infection,
but very little IL-4 at the early time points. By day 28 postinfectio
n, however, splenocytes from Mf-infected mice showed some IL-4 secreti
on in response to specific Ag (40 U/ml). The IFN-gamma response to Mf
was found to be independent of the inoculum dose in the range of 10(2)
to 10(6) organisms. In contrast, splenocytes taken from adult worm-im
planted mice on days 14, 21, and 28 postinfection produced high levels
of IL-4 (up to 435 U/ml) and negligible amounts of IFN-gamma despite
the production of large numbers of Mf by adult female worms. CD4(+) ce
lls were primarily responsible for this IL-4 production. These results
demonstrate that adult filarial parasites, and females in particular,
exert a rapid polarization of the immune response in a Th2-like direc
tion, but that this effect may be modulated by the Mf stage.