HYPERDIPLOIDY AND TRISOMY OF CHROMOSOME-15 IN PERITONEAL-MACROPHAGES OF HYPERIMMUNE, OLDER SWISS MICE

Chromosome analysis was carried out in resident and exudate peritoneal macrophages and, also, in bone marrow cells of groups of mice either immunized with ovalbumin in complete Freund's adjuvant and challenged with the antigen, or stimulated with the irritant thioglycollic acid. Labeling of the phagocytic cells with colloidal carbon showed that dividing cells in the peritoneal cavity of experimental mice are resident macrophages. Also shown was an increase in number of hyperdiploid metaphases in hyperimmune, older mice but not in the young ones. Statistical analysis showed these differences to be significant. G-banding of hyperdiploid cells of hyperimmune older mice showed trisomy of chromosome 15 in several metaphases analyzed. The absence of hyperdiploid metaphases in the bone marrow cells of hyperimmune mice and in exudate macrophages of mice that received the irritant thioglycollic acid suggests that hyperdiploidy occurs in resident macrophages in the peritoneal cavity but not in their precursors in the bone marrow. These results raise some questions such as, hyperimmune older mice resident macrophages being prone to hyperdiploidy and trisomy of chromosome 15.