Growth and sexual maturity were compared among Monterey Botryllus schlosseri colonies cultured in the laboratory and in Monterey Marina in two separate studies: Phase I April to July 1984, a time when Botryllus growth is rapid in the field, and Phase II December 1984 to March 1985, a time when growth is minimal in the field. Laboratory colonies were kept in tanks of standing, aerated filtered seawater at 15C, 20C, and 24C; the seawater was changed daily or on alternate days. Food types were two concentrations of an algal mixture and five concentrations of Liquifry, a commercially available food for filter-feeding marine invertebrates. All algae-fed colonies did poorly. During Phase I, the colonies kept in Monterey Marina grew much faster than those in the laboratory, but they took longer to reach sexual maturity than the Liquifry-fed colonies grown at 20C and had a lower survivorship. In Phase II, Botryllus growth rates and survivorships in seven of the eight laboratory treatments were better than those of marina colonies. These laboratory treatments yielded a substantial proportion of sexually mature colonies, whereas none of the marina colonies produced eggs during Phase II.

To determine whether Monterey Botryllus and Woods Hole Botryllus are the same species, comparisons were made of their morphology, biology, and colony specificity. In addition, matings were carried out to ascertain whether fertile [Monterey x Woods Hole] F1 progeny could be obtained. The morphology and biology of Botryllus colonies from Monterey and from Woods Hole are very similar, and fertile F1 progeny were obtained from interpopulation crosses. Therefore, we conclude that Monterey and Woods Hole Botryllus belong to the same species. However, slight differences were observed in the allorecognition reactions (colony specificity) of these two populations. Although there are some inconsistencies among the descriptions of Botryllus schlosseri and further extensive studies of Botryllus taxonomy are needed, our data indicate that Botryllus from Monterey and from Woods Hole may be designated contingently as B. schlosseri.

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24 monoclonal rat antibodies are described that are reactive with determinants encoded by the major histocompatibility complex (MHC) of the rat. These hybridoma antibodies were derived by fusing mutant mouse myeloma cells to spleen cells from Lewis rats immunized with allogeneic Brown Norway cells. All 24 antibodies are cytotoxic for both Brown Norway target cells and target cells from the appropriate MHC congenic rats. Pattern of cytotoxicity and hemagglutination strongly suggest reactivity against class I (K or D equivalent) rat MHC determinants. Cytotoxic cross-reactivity patterns were generated for each monoclonal antibody on a panel of rat and mouse lymphoid cells and human peripheral T lymphocytes. A high degree of interspecies cross-reactivity was noted with approximately one-half of the antibodies positive on human and/or mouse target cells. 11 antibodies recognized polymorphic determinants in the mouse, and, by using target cells from MHC congenic mouse strains, it was shown that these determinants are encoded by genes within the H-2 complex. Finally, by considering the overall reactivity patterns of these monclonal antibodies on all target cells, one can show that these 24 antibodies represent a minimum of 14 antibody specificities.

Two monoclonal rat anti-MHC alloantibodies detect a polymorphic determinant expressed on the peripheral lymphocytes of normal human donors. The pattern of cytotoxicity observed with these antibodies correlated with the HLA type of the individual; no HLA-A-locus specificities showed significant associations, and all of the HLA-B-locus specificities showing significant association were members of the Bw6 supertype. Family studies established that the determinant detected by the monoclonal antibodies is linked to HLA. These studies therefore provide an alternative basis for the production of monoclonal antibodies to polymorphic HLA determinants based on the conservation of polymorphic MHC determinants between man and rats.