PREVENTION OF FETAL LOSS IN EXPERIMENTAL ANTIPHOSPHOLIPID SYNDROME BYINVIVO ADMINISTRATION OF RECOMBINANT INTERLEUKIN-3

Antiphospholipid antibodies are strongly associated with arterial and venous thrombosis and with fetal loss. Recently an experimental model for antiphospholipid syndrome (APLS) was established in our laboratory . In this model, mice are immunized passively or actively with anticar diolipin antibodies and acquire the syndrome, which is characterized b y prolonged activated partial thromboplastin time (APTT), thrombocytop enia, low fecundity rate, and fetal loss. In a normal process of pregn ancy, lymphokines affect fetal implantation and development. Cytokines from the colony stimulating factor family, like GM-CSF and IL-3, were shown to be positive signals for implantation and to promote placenta l development and fetal growth. Given our preliminary findings of low IL-3 in mice with APLS and the efficacy of IL-3 in preventing fetal lo ss in a strain of mice prone to fetal resorption, our aim in the prese nt study was to examine the effect of murine recombinant IL-3 (mrIL-3) on pregnant mice induced with experimental APLS. Mice were passively transfused to the tail vein, 24 h following mating, with anticardiolip in antibodies. The mice were divided into two groups: one group was in jected intraperitoneally with mrIL-3 on days 6.5, 8.5, and 10.5 after mating, while the control group was injected with PBS. When the mice w ere killed on day 15 of pregnancy a 32%+/-4.2 resorption rate was obse rved in the anti-cardiolipin-immunized group, which was reduced to 4%/-0.3 following treatment with mrIL-3. The thrombocytopenia associated with the experimental APLS was also corrected following lymphokine ad ministration. IL-3 may be effective in prevention of recurrent fetal l oss in APLS.