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Infect. Immun., Dec 1997, 5052-5056, Vol 65, No. 12
BA Garvy, JA Wiley, F Gigliotti and AG Harmsen
To determine whether different antibody isotypes associated with T helper 1
(Th1) or Th2 responses are protective against Pneumocystis carinii, mice
with disrupted interleukin 4 genes (IL-4(-/-) mice) or gamma interferon
genes (IFN-gamma(-/-) mice) along with wild-type C57BL/6 mice were
immunized intratracheally against P. carinii, depleted of T cells in vivo
by use of monoclonal antibodies, and rechallenged intratracheally with
10(7) viable P. carinii organisms. Nearly all immunized mice resolved their
lung P. carinii infections (limit of detection, log10 4.06) within 21 days
of challenge even though they were depleted of T cells. Unimmunized mice
depleted of T cells had significant lung infections (>log10 5.5) at day
21 post-P. carinii challenge. IFN-gamma(-/-) and wild-type mice developed
P. carinii-specific immunoglobulin primarily of the immunoglobulin G1
(IgG1) subclass with relatively little P. carinii-specific IgG2a, IgG2b, or
IgG3 in their sera, characteristic of a Th2-type response. In contrast,
IL-4(-/-) mice had primarily an IgG2b P. carinii-specific antibody response
in their sera with very little IgG1. Although IgG2b was the predominant
isotype in IL-4(-/-) mice, optical density values of IgG2a and IgG3 were
significantly higher in these mice (two and three times, respectively) than
in IFN-gamma(-/-) mice, characteristic of a Th1-type response. Together,
these data indicate that resolution of P. carinii infection can be mediated
by specific antibody responses and that the antibody response can be either
a predominantly Th1 or Th2 type. Furthermore, although wild-type mice
mounted a Th2-like antibody response, IL-4(-/-) mice could resolve P.
carinii pneumonia, indicating that resistance to P. carinii can occur in
the absence of IL-4.
Copyright © 1997, American Society for Microbiology
Protection against Pneumocystis carinii pneumonia by antibodies generated from either T helper 1 or T helper 2 responses
Trudeau Institute, Saranac Lake, New York 12983, USA. bgarvy@northnet.org
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