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In the previous paper, the present authors reported on diminution in agglutinability of trypsin-treated M and MN red cells with anti-M IgG antibody. This paper deals with the time course of changes in agglutinability and quantitative differences of M agglutinogen of red cells. M agglutinogen of M red cells disappeared much faster than that of MN, and the lowest titer of anti-M IgG antibody to agglutinate M red cells was higher than that to agglutinate MN red cells. The significant difference of agglutination scores was observed in the frequency distribution in 100 cases of M and MN red cells each. Subgroups such as M1 and M2 in M agglutinogen of trypsin-treated red cells reacting with anti-M IgG antibody were unsettled.

The agglutinability of the proteolytic enzyme treated M, N and MN red cells with any one of the anti-M and -N antisera, eluted antibodies and class antibodies was studied. The enzyme-treated 141 and N red cells lost their group specificity in agglutination with the absorbed antisera. However, it was noted that the enzyme-treated M red cells acquired N agglutinogen instead of losing their own M agglutinogen in agglutination with the eluted antibodies. The enzyme-treated N red cells maintained the group specificity. Agglutination of the enzyme-treated red cells with the class antibodies showed clearly that the changes in agglutinability of the red cells were caused by each of the class antibodies.

It was reported previously that proteolytic enzyme-treated M red cells lost their reactivity completely with only anti-M IgG antibody. In this paper, M red cells treated with trypsin for 45 min or 3 hr were used to prepare group-specific anti-M IgG and -N IgG antibodies as an adsorbent. It was revealed that M red cells treated for 3 hr could adsorb anti-N antibody in anti-M IgG fraction obtained from crude anti-M serum by DEAE-cellulose column chromatography. The potency of the red cells to adsorb anti-N IgG antibody was similar to that of normal N red cells. Anti-N IgG antibody was prepared by heat-eluting trypsin-treated M red cells sensitized with anti-N fraction. However, the experiments with M red cells treated for 45 min showed unsatisfactory results. It was due to the red cells which could still react with high-titered anti-M IgG antibody but not sufficiently with anti-N IgG antibody.

This paper deals with MN blood grouping of stains of organ homogenate and thin organ sections by means of an elution test in combination with antiglobulin test. Each stain of the liver, spleen, brain, heart, lung, thyroid, kidney and muscle homogenates gave evidently M and N blood group activities in accordance with those of sources. It was considered that non-specific adsorbing potency of the human organ was eliminated in the procedure of homogenate-staining. However, examination on sections showed frequently unsatisfactory results. It was attributed to non-specific adsorption of sections with anti-M and -N antibodies. The present findings may offer a valuable information to identify human tissues in forensic practice.