GENETICS OF A GAMMA GLOBULIN ISOANTIGEN (ALLOTYPE) IN THE MOUSE

The early history of Stanford Immunology

From its 1960 beginnings in a pair of windowless Genetics Department laboratories under the Stanford Medical School Dean's Office to its current broad-based program, which joins faculty members from departments across the Medical School, the Stanford Immunology Program has played a central role in shaping both basic and clinical immunology thinking. In this article, we tell the story of the beginnings of this odyssey in a reminiscence-based format that brings the flavor of the time in the words of people who lived and built the history.

THE IMMUNOGLOBULINS OF MICE. I. FOUR MAJOR CLASSES OF IMMUNOGLOBULINS: 7S GAMMA-2-, 7S GAMMA-1-, GAMMA-1A (BETA-2A)-, AND 18S GAMMA-1M-GLOBULINS

Two classes of 7S γ-globulins are identified in normal mouse serum and are designated 7S γ₂-globulins and 7S γ₁-globulins. These two immunoglobulin classes are similar in size. They differ in range of electrophoretic mobility, in specific antigenic determinants, and in genetically determined isoantigens. Four classes of immunoglobulins in mouse serum, i.e. 7S γ₂-, 7S γ₁-, γ_1A (β_2A), and γ_M-globulins, were shown to have antibody activity. Each class was characterized and shown to have distinctive immunochemical and physicochemical properties. The genetically determined isoantigens, Iga-1 and Iga-2, were shown to be present only on 7S γ₂-globulin molecules.

IMMUNOGLOBULIN ISOANTIGENS (ALLOTYPES) IN THE MOUSE. I. GENETICS AND CROSS-REACTIONS OF THE 7S GAMMA-2A-ISOANTIGENS CONTROLLED BY ALLELES AT THE IG-1 LOCUS

Eight antigens of 7S γ₂-immunoglobulins controlled by alleles at a single locus Ig-1, have been identified in mice. This locus has previously been shown to determine antigenic specificities on the F fragments of 7S γ_2a-globulins. The reactions of these antigens with various isoantisera have shown that the antigens all cross react with one another. New methods for the analysis of antigenic specificities of soluble proteins are presented in detail. A sensitive method for detecting in the order of 0.01 µg of these isoantigens has been developed, based on the quantitative inhibition of precipitation of I¹²⁵-labeled antigen. Cross-reactions of the antigens were analysed in inhibition assays and the data is compatible with the existence of a minimum of eight antigenic specificities. Each of the antigens is composed of different combinations of these specificities, with only one antigen having a specificity not present in any other. Sixty-eight mouse strains have been tested with specific isoantisera, and on the basis of the results, have been placed into the eight allele groups. Evidence for close genetic linkage of the Ig-1 locus and 11 chromosome markers has been sought and not found.

DISTRIBUTION, INHERITANCE, AND PROPERTIES OF AN ANTIGEN, MUB1, AND ITS RELATION TO HEMOLYTIC COMPLEMENT

An antigen, MuB1, present in the sera of some mice, can elicit a precipitating antibody in certain other strains of mice. An antibody to the antigen MuB1 can also be elicited in rabbits. 99 strains and substrains of inbred mice were tested for the presence of MuB1; the antigen was found in the sera of 44 strains (61 per cent) and 14 DBA substrains (52 per cent). Evidence is presented indicating that mice lacking MuB1 do not make a modified antigen, corresponding to MuB1, but are genetically deficient in synthetic ability at this site. By reaction with antibody to MuB1 an antigen corresponding to MuB1 was found in 13 of the 15 orders of mammals, and in 63 of 85 mammalian species tested, including man and guinea pig. The quantity of the antigen MuB1 is always greater in the serum of male than in the serum of female mice. The concentration of MuB1 increases with age; this increase is more marked in male than in female mice. By means of backcross experiments it was shown that the inheritance of MuB1 is unifactorial, is independent of the inheritance of the gamma globulin allotype MuA2, and is qualitatively independent of the sex of the parents. The antigen MuB1 is found in the euglobulin fraction of serum; it loses its ability to precipitate with antibody after heating at 56°C, but not after treatment with ammonia or hydrazine. By gel filtration, MuB1 is separated with a fraction containing molecules of molecular weight ≈ 150,000. An empirical correlation was observed between the presence or absence of MuB1 in the sera from inbred mice and the presence or absence of hemolytic complement (Hc), as measured by a test using a high concentration of rabbit hemolysin. In backcross experiments also, a correlation between hemolytic complement and the presence of MuB1 was demonstrated. As with MuB1, male mice had a higher hemolytic complement level than females. The particular component of complement which may be identical with MuB1 has not been identified.

Mouse immunoglobulin allotypes: detection with rabbit antiserums

An antiserum with allotypic specificity for mouse gamma(2a)-globulins was prepared in a rabbit by injection of 7S gamma(2)-globulin of C(57)BL/6 mice. The antibody reacted with an isoantigen in the 7S gamma(2)-globulins of normal serum of mouse strains belonging to the lg-1(b) allotype class (C(57)BL/6, C(57)BL/10, and SJL strains). No precipitin reaction was observed with serum from 18 other inbred mice strains representing other lg-1 allotype classes.

Genetics of MuB1 and of a complement defect in inbred strains of mice

A mouse antigen, MuB1, has been shown by the study of backcrosses to be inherited in a unifactorial dominant manner. Its inheritance is not linked with gamma globulin allotypes, but has been shown to be linked with the presence of the haemolytic complement system. The concentration of MuB1 in the serum of several inbred strains of mice showed sex-associated differences; however, the presence of MuBl did not depend on the sex of the parents or on the sex of the offspring. The inheritance of antibody responsiveness is discussed in terms of the inheritance of the antigen, MuB1.

Linkage in Control of Allotypic Specificities on Two Different ggrG-Immunoglobulins

Allotypic specificities were identified on two different myeloma proteins and the corresponding normal gammaG-immunoglobulins of BALB/c mice. When the sera of F(2) progeny from a cross between BALB/c mice having the a1 allotype and AL mice having the a4 allotype were tested for these specificities, it was found that the two allotypic specificities of the BALB/c mice were either both present (87 mice) or both absent (36 mice), an indication of linkage in their genetic control.

MOLECULAR AND SUBMOLECULAR LOCALIZATION OF TWO ISOANTIGENS OF MOUSE IMMUNOGLOBULINS

Three related classes of immunoglobulins ( 7S gamma(-), beta(2)A(-), and gamma(1)M(-) globulin) in normal C3H and C3H and C57BL/6 mouse serums were isolated and examined for the isoantigens Iga-1 and Iga-2. The results indicate that the genetic locus determining the Iga-1 and Iga-2 antigens affects only a portion of the normal mouse immunoglobulin population (that is, 7S gamma-globulin) and only the gamma-specific part ("F" piece) of the 7S gamma-globulin molecule.