Hybrid genes were constructed for the localization of allodeterminants on murine class I antigens recognized by antibodies and cytol ytic T lymphocytes. By using deletion subclones of the H12K and H-2Kk genes, homologous regions were exchanged between the two alleles. The altered genes were introduced and expressed in mouse fibroblast and fibrosarcoma cells. Cells expressing hybrid antigens were analyzed with 29 monoclonal anti-H-2Kd and anti-H-2Kk antibodies and with 150 short-term alloreactive cytolytic T-cell clones. When only the first or only the second amino-terminal domain was exchanged, most T cells and 60% of the antibodies lost their reactivity to the H-2K antigen. No T-cell clone was directed against the third extracellular domain, whereas three antibodies could bind to this domain. This implies that nearly all determinants essential for a cytolytic T-cell response or for antibody binding lie on the two external domains and are conformational structures generated by the interaction of these two domains.
We and others have previously reported that homologous exchange of alpha 1 or alpha 2 domains between different alleles led to loss of most determinants recognized by cytotoxic T lymphocytes (CTL) raised against the parental H-2 class I antigens. Here we demonstrate that exchange of alpha 1 or alpha 2 domains between the Kk and Kd allele results in the formation of neodeterminants against which allospecific CTL can be generated in responder mice of various related and unrelated H-2 haplotypes. In fact, only CTL against the neodeterminants on the hybrid molecules were found and none against the parental Kk and Kd determinants. In addition our data show that recognition of the neodeterminants is H-2 unrestricted. These findings suggest that in the hybrid molecules the basic structure of a major histocompatibility complex molecule has been preserved although most parental allodeterminants on the alpha 1 and alpha 2 domains have been modified.
During development of Acanthamoeba castellanii in a non‐nutrient medium, the pattern of synthesis of proteins changes. Comparison of in vivo and in vitro patterns of protein synthesis reveals concomitant relative increases of five proteins, indicating a control of synthesis of these proteins at the level of the RNA content. The decrease in the overall rate of protein synthesis and relative decreases in the synthesis of actin and ribosomal proteins during development, not accompanied by equivalent changes in the content of mRNA, suggest control mechanisms also at the level of translation. Patterns of ribosomal proteins do not change qualitatively during encystation, indicating that the inhibition in the overall rate of protein synthesis and the formation of inactive monosomes is not controlled by this mechanism; however, phosphorylation of one ribosomal protein, S 3, is observed occasionally during encystation. Phosphorylation of S 3 is also detected after transfer of stationary phase cells into fresh nutrient medium. It was found that only such cells having RNA of aberrant properties are able to phosphorylate S 3 after transfer into fresh nutrient medium. Since these changes in the property of RNA are never observed in cysts, in which phosphorylation of S 3 sometimes occurs, it is concluded that either other alterations in the properties of RNA than those detected or other parameters are responsible for changes in phosphorylation of S 3.
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