Anti-i cold agglutinins in choriocarcinomatosis: trophoblastic i antigen.

The fetal antigen i has been demonstrated by indirect immunofluorescence on cord erythrocytes and placental trophoblast. A patient with disseminated choriocarcinoma developed high-tire anti-i cold agglutinins, and minor elevation of anti-i titres was seen in four out of six further patients with treated choriocarcinoma. In normal pregnant women, 6% showed similar increases in anti-i titres.