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Population distribution and inheritance pattern were analyzed in mink IgG allotypes: L1 (L chains), H2, H3, H4, H6, H7, and H8 (the constant region of the H chains, i.e. C gamma-allotypes) and conformational allotype 5 with unknown chain localization. Contrary to expectation, neither allelism, nor close linkage were demonstrated for these allotypes. The major feature of the inheritance of H2, H3, and H4 C gamma-allotypes, as well as allotype 5, was significant excess of negative (without these allotypes) progeny in the F1 generation from monohybrid cross. The explanation offered for this departure of the C gamma-allotypes from normal Mendelian genetics suggests widespread latencies of their expression in mink.

By means of intraspecific immunization of domestic mink (Mustela vison Schr.), 8, in all probability, complex IgG allotypes were detected in their sera. Based on the results of analysis of the preparations of the IgG heavy (H) and light (L) chains, as well as proteolytic IgG fragments, we assigned the allotypes detected to three groups: (1) marker of the L chain, L1; (2) allotypes of the C region of gamma-chains (H2, H3, H4, H6, and H8) and conformational allotype H7; (3) conformational allotype 5 with unknown location on the chains.

Diploid-triploid chimeras have been observed both in man and in a number of laboratory and livestock animals. The mechanism(s) of their origin remains enigmatic. One approach is to calculate for each proposed mechanism the expected frequencies of zygotes bearing different gonosomic complements in the two cell lines. Observed samples are then compared with the expectations. The mechanisms that have been considered include: (1) fertilization of a blastomere, (2) absorption of the second polar body into a blastomere, (3) fertilization of the first polar body, (4) independent fertilization of both nuclei in binucleated oocytes, (5) fertilization of the second polar body as well as the egg, and (6) fusion of two eggs. The sample of minks comprised three preimplantation embryos, nine postimplantation embryos, and three neonatal pups, with gonosomic complements of 7 XX/XXX, 3 XX/XXY, 4XY/XXY, and 1 XY/XYY; the chicks comprised 13 embryos at 1 day of incubation, 1 embryo at 4 days, and one adult bird, with gonosomic complements of 5 ZZ/ZZZ, 1 ZZ/ZZW, 1 ZW/ZZZ, 3 ZW/ZZW, and 5 ZW/ZWW. If it is assumed that within each species all, or most, of the 2n/3n chimeras arise from the same mechanism, then the occurrence of a type that has an expected frequency of zero for a given proposed mechanism effectively eliminates that mechanism as a source. All of the chicks could have resulted from only one mechanism, viz., independent fertilization of both nuclei in binucleated oocytes. The sample of minks could have resulted from the same mechanism or from fertilization of a blastomere of a two-cell, 2n embryo.

Quantitative expression of C gamma-allotype H4 of mink immunoglobulins was studied by enzyme-linked immunosorbent assay. The results presented suggest that production of H4 is under specific regulation. the concentration of H4 varies three orders of magnitude (10-10,000 micrograms/ml) from one mink to another. Fifteen percent of the sera of normal minks have the low H4 concentration, undetectable by the standard procedure of double immunodiffusion routinely used to test mink IgG allotypes. However, expression of these 'minor' allotypes may be significantly enhanced by hyperimmunization. Instability of this kind seems to be the main cause of earlier described deviations from Mendelian inheritance of C gamma-allotypes H2, H3 and H4.

A new allotype of the mink light chains, designated L3, was identified. This allotype is inherited as a Mendelian character at a frequency of 0.46 in the mink population. Data were obtained indicating that L3 is independent of the C gamma-heavy chain allotypes of mink immunoglobulins. The gene L3 is closely linked to a gene encoding L1, another light chain allotype. Alloantigens L1 and L3 are presumably markers of the light chains of two different subtypes. In contrast to L1, which occurs in many mammalian species, L3 is species-specific, i.e., it is a case of light chain polymorphism representative of the whole mink species.