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Two murine monoclonal antibodies, 2A3D2 and 2D11E2 (both IgM), which are directed to the gangliosides and sialoglycoproteins related to a rare blood group antigen, Cad, were obtained by using a ganglioside mixture prepared from human hepatocellular carcinoma cells (PLC/PRF/5) as the immunogen. These two monoclonal antibodies detected multiple ganglioside antigens present in the PLC/PRF/5 cells, and the major antigenic ganglioside was characterized as IV4GalNAc beta-GD1a, which has the carbohydrate structure GalNAc beta 1----4(NeuAc alpha 2----3)Gal beta 1----3GalNAc beta 1---- 4(NeuAc alpha 2----3)Gal beta 1----Cer. The two antibodies also reacted with GM2 (GalNAc beta 1----4[NeuAc alpha 2----3]Gal beta 1----4Glc beta 1----Cer) and a Cad-active lactoseries ganglioside (IV4GalNAc beta-sialosylparagloboside, GalNAc beta 1----4[NeuAc alpha 2----3]Gal beta 1----4GlcNAc beta 1---- 3Gal beta 1----4Glc beta 1----Cer), which have carbohydrate structures related to IV4GalNAc beta-GD1a. Beside gangliosides, both antibodies recognized the carbohydrate determinant carried by glycophorin A on very rare Cad-positive human RBC; the structure of which is GalNAc beta 1----4(NeuAc alpha 2----3)Gal beta 1----3(NeuAc alpha 2---- 6)GalNAc alpha 1----Ser/Thr. From these findings, it is clear that monoclonal antibodies 2A3D2 and 2D11E2 both recognize the nonreduced carbohydrate terminus composed of three sugar residues, GalNac beta 1----4(NeuAc alpha 2----3)Gal beta 1----R, and are useful for detecting the Cad-related antigen in cells and tissues. By using these monoclonal antibodies, it was revealed that many cultured human hepatocellular carcinoma cell lines and cancer tissues taken from patients with hepatocellular carcinoma contain both Cad-active glycoprotein antigens and related gangliosides, while normal liver tissues contain no appreciable amount of either species of antigen. The Cad-active glycoprotein antigens in cultured human hepatocellular carcinoma cells appeared as triplet bands having molecular weights of 92,000, 75,000, and 61,000, under either reducing or nonreducing conditions in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Essentially the same triplet proteins were observed in as many as 4 of 9 cases (44%) of cancer tissue from patients with hepatocellular carcinoma, but not in neighboring cirrhotic tissues or normal livers tissues. These results suggest that the rare blood group antigen Cad is associated with human cancers, especially hepatocellular carcinoma.

Two Japanese propositi with the rare Gerbich -negative (Ge-) phenotype were found by screening serum of donors for antibodies. These are the first two examples of Ge negative in Japanese. Both had the Gerbich type of Ge-negative phenotype (Ge: -1, -2, -3,), showed some depression of Kell system antigens, and had anti-Ge in their sera. The parents of each of the propositi were first cousins, and one of the propositi had two Ge-negative siblings.

A new low-frequency red cell antigen, OSa, in a Japanese blood donor is inherited as a Mendelian dominant. A family study showed that OSa is not controlled by ABO, P1, Rh, Kidd, or Diego loci, nor is the antigen X- or Y-borne.

'Naturally occurring' anti-Kell (K1) was found in a Japanese male who has never received a transfusion. The antibody agglutinated K:1 cells suspended in saline at 4 and 22 degrees C as well as cells suspended in albumin and treated with proteolytic enzymes.

Two patients and a healthy blood donor were found to be Lan negative and to have anti-Lan in their sera. These are the first three examples of the Lan-negative phenotype to be described in Japanese. The families of two of the propositi were studied: the parents of both were first cousins and one of the propositi had a Lan-negative sibling. No Lan-negative examples were found in 15,000 Japanese donors screened with anti-Lan.

The antigen corresponding to the 'new' allele Kpc postulated in a Japanese family is the low frequency antigen Levay recognized in England 33 years ago.

An antibody found in the serum of a Japanese blood donor detects a new high-frequency red cell antigen named UMC. UMC is absent from Inab phenotype cells, weakly expressed on Dr(a-) cells, and destroyed by alpha-chymotrypsin but not trypsin treatment of red cells. UMC is, therefore, a Cromer-related antigen. Immunoblotting with anti-UMC showed that UMC antigen, in common with other Cromer-related antigens, is carried on a red cell surface glycoprotein with an apparent molecular weight of 70,000, which presumably is the complement regulatory protein decay-accelerating factor.

Four Kp(a-b-) Japanese sisters, the product of a consanguineous mating, have otherwise normal Kell antigens. Kpc, a 'new' allele of Kpa and Kpb is the most probable background.

Fourteen Jk(a-b-) persons were detected by testing 638,460 Osaka blood donors with an automated 2 M urea technique. Two of these 14 Jk(a-b-) samples were quite different from the hitherto reported Jk(a-b-) phenotype, and a family study showed that the mode of the inheritance was dominant. The red cell membranes of these Jk(a-b-) samples were studied by polyacrylamide gel electrophoresis and unusual protein bands (apparent mw, 67,000 d) were detected.

The low-frequency red cell antigen NFLD was identified in 2 Japanese donors. A family study showed that the antigen is not part of the P1 blood group system. Anti-NFLD was found in serum of several donors (frequency of 0.044%).