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Infection and Immunity, June 2000, p. 3297-3304, Vol. 68, No. 6
Department of Bacteriology and Medical
Mycology1 and Department of Veterinary
Medicine,3 Istituto Superiore di
Sanità, Rome, and Department of Pharmacological
Sciences and Experimental Medicine, University of Camerino,
Camerino,2 Italy
Received 13 December 1999/Returned for modification 27 January
2000/Accepted 17 March 2000
Humoral (antibody [Ab]) and cellular Candida-specific
immune responses in the vaginas of pseudoestrus rats were investigated during three successive infections by Candida albicans.
After the first, protective infection, Abs against mannan and aspartyl proteinase antigens were present in the vaginal fluid, and their titers
clearly increased during the two subsequent, rapidly healing infections. In all animals, about 65 and 10% of vaginal lymphocytes (VL) were CD3+ (T cells) and CD3
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Copyright © 2000, American Society for Microbiology. All rights reserved.
Local Anticandidal Immune Responses in a Rat Model of Vaginal
Infection by and Protection against Candida
albicans
CD5+ (B cells), respectively. Two-thirds of the
CD3+ T cells expressed the
/
and one-third expressed
the
/
T-cell receptor (TCR). This proportion slightly fluctuated
during the three rounds of C. albicans infection, but no
significant differences between infected and noninfected rats were
found. More relevant were the changes in the
CD4+/CD8+ T-cell ratio, particularly for cells
bearing the CD25 (interleukin-2 receptor
) marker. In fact, a
progressively increased number of both CD4+
/
TCR and
CD4+ CD25+ VL was observed after the second and
third Candida challenges, reversing the high initial
CD8+ cell number of controls (estrogenized but uninfected
rats). The CD3
CD5+ cells also almost doubled
from the first to the third infection. Analysis of the cytokines
secreted in the vaginal fluid of Candida-infected rats
showed high levels of interleukin 12 (IL-12) during the first infection, followed by progressively increasing amounts of
IL-2 and gamma interferon during the subsequent infections. No IL-4 or
IL-5 was ever detected. During the third infection, VL with in vitro
proliferative activity in response to an immunodominant mannoprotein antigen of C. albicans were present in the
vaginal tissue. No response to this antigen by mitogen-responsive
blood, lymph node, and spleen cells was found. In summary, the presence of protective Ab and T helper type 1 cytokines in the vaginal fluids,
the in vitro proliferation of vaginal lymphocytes in response to
Candida antigenic stimulation, and the increased number of activated CD4+ cells and some special B lymphocytes after
C. albicans challenge constitute good evidence for
induction of locally expressed Candida-specific Ab and
cellular responses which are potentially involved in anticandidal protection at the vaginal level.
*
Corresponding author. Mailing address: Department of
Bacteriology and Medical Mycology, Istituto Superiore di Sanità,
Viale Regina Elena, 299, 00161 Rome, Italy. Phone: 39-06-49387113. Fax: 39-06-49387112. E-mail: cassone{at}iss.it.
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