Prevention of spontaneous abortion in the CBA x DBA/2 mouse model by intravaginal TGF-beta and local recruitment of CD4+8+ FOXP3+ cells.

PROBLEM: Activation of latent transforming growth factor (TGF)-beta in seminal plasma has been suggested by Robertson et al. to promote maternal tolerance to paternal antigens. A possible consequence reported by Tremellen et al. is increased pregnancy rates in women undergoing IVF. A decreased spontaneous abortion rate has also been postulated. Seminal plasma contains many factors besides TGF-beta, and a critical test of the hypothesis was required. The purpose of the present study was to directly test the effect of pure TGF-beta.

METHOD OF STUDY: Pharmaceutical grade bioactive TGF-beta3 with a bovine serum albumin (BSA) carrier 0.1-1% in phosphate-buffered saline (PBS) was given into the vaginal tract of CBA/J female mice at the time of mating with DBA/2 males. One microgram Salmonella enteritidis lipopolysaccharide was given intraperitoneally to augment occult losses and spontaneous resorptions assessed on day 13.5 of pregnancy. The effect of TGF-beta3 on recruitment of lymphomyeloid cells to the vaginal wall and vaginal lumen of unmated mice in estrus was assessed using immunohistochemistry and flow cytometry.

RESULTS

Two nanogram of intravaginal TGF-beta3 in 0.1% BSA-PBS or 20 ng in 1% BSA-PBS reduced abortion rates. Protection was comparable to that achieved by immunization with BALB/c spleen cells. Fraction V BSA, a binder of TGF-betas, had some activity, and could reduce availability of added TGF-beta3. CD11c dendritic cells, CD3+ T cells, and CD25+ cells were recruited to the vaginal wall by 48 hr after TGF-beta3 treatment, and cellularity of vaginal exudates increased. Foxp3+ cells were present in increased numbers, and appeared to be CD8+ and CD4+ 8+. Semen, but not TGF-beta3, stimulated a physiological polymorphonuclear leukocyte exudate.

CONCLUSION

Intravaginal bioactive TGF-beta3 can enhance success of pregnancy in vivo in an established model of abortion. The result could be explained by the independent ability of TGF-beta to promote a regulatory T-cell response.