The Determination of Hereditary Antigenic Differences in Genically Identical Paramecium Cells

Abstract

In stock 51 of variety 4 of P. aurelia there are more than 6 antigenically diverse hereditary types. Of 6 types so far isolated from stock 29, 4 correspond to types A, B, C, and D in stock 51. Each of the new antigenic types (E, G, F and H) as well as A, B, C and D and the stock 29 homologues of the latter are immobilized only by the corresponding one of the 8 types of dilute antiserum. This is followed by transformation from one type to another. The transformed animals yield cultures that remain true to type but when interbred there is no segregation in F2 and type strictly follows the cytoplasm. Transformation back to the old type by exposure to the new serum is possible in each instance; there is thus no complete loss of antigenic possibility. Each type possesses the capacity to produce all the types of the stock to which it belongs. Directing the transformation by combining exposure to immobilizing serum with other conditions has been tested in respect to diverse temperatures and amount of food. Decrease of temperature and amt. of food have similar effects. If type D of stock 29 is exposed to anti-D serum at 32[degree] in the presence of an excess of food, 94% transform to Type B, but 96% transform to Type H at 20[degree] in the absence of food. Even without immobilizing antiserum, similar directed transformations occur; in stock 51 at 32[degree], type A remains constant and all others transform to A, but at 12[degree] B remains constant and other types transform to B. At 27[degree] with enough food added to permit one fission daily, all types, regardless of origin, are constant and hereditary, In crosses of the 2 stocks there was 1:1 segregation in F2 clones of type F or ability to yield type F (which exists only in stock 29). Type F thus depends upon a gene. Thus cytoplasmic control of the antigenic diversity within a stock is ultimately gene-dependent as well as environment-dependent. The foregoing relations are interpreted on the hypothesis that each antigen is, or is detd. by, a plasmagene producible under gene action. Diversity of cell types in the Metazoan as well as Protozoan may arise as a result of environmentally produced quantitative differences among a series of alternative plasmagenes.