Although the pathophysiological mechanisms leading to recurrent
spontaneous abortion are still not fully understood, treatment schemes based on immunological principles have been advocated in recent years claiming that the production of the so-called
blocking factor is being specifically stimulated. We investigated, retrospectively, whether active immunization can affect the production of
immunoglobulin (Ig)G and
IgM anticardiolipin antibodies. In a group of untreated recurrent
spontaneous abortion patients (n = 9), the range of variation of
cardiolipin antibodies, during consecutive controls taken at the same time interval as after immunization, was not statistically significant. In contrast to this, significant increases of both
IgG and
IgM antibodies occurred after active immunization with paternal leucocytes in 10 of 15, and in 6 of 15 cases, respectively. The mean basal and posttransfusion levels were: 7.26 +/- 2.53 and 30.15 +/- 23 U/mL for
IgG and 2.26 +/- 1.2 and 6.82 +/- 5.6 U/mL for
IgM, respectively. We conclude that active immunization with human lymphocytes leads to the production of
antibodies against
cardiolipin. This effect is exerted on both
IgM and
IgG antibodies.