Immunobiological properties of a concanavalin A derivative

Induction of suppressor cells, interleukin-2 production and mitogenesis with monomeric concanavalin A: different actions of tetrameric and monomeric concanavalin A

The ability of a photoalkylated monomeric concanavalin A (Con A) derivative to induce mitogenesis, interleukin-2 (IL-2) production and suppressor cells in murine spleen cell cultures has been compared with the activity of native, tetrameric Con A. The monomeric derivative was prepared by photochemically induced alkylation of tryptophan residues of tetravalent Con A in the presence of chloroacetamide followed by sizing chromatography [Tanaka et al. (1981) J. Biochem. 89, 1643-1646]. The monomeric derivative appeared to display less mitogenic activity than the tetramer and was also less effective in inducing IL-2 production. No difference was detected between the monomeric and tetrameric forms of Con A in inducing suppressor cells. The data suggest that cross-linking and bridging via sugar-binding sites, while potentiating mitogenesis and IL-2 production, had little effect on suppressor cell induction.

Lectin-like activity from Persea americana

An extract from the seeds of Persea americana possessed an erythro-agglutinating activity. The agglutinin was devoid of specificity for carbohydrates, but interacted readily with basic proteins or basic polyamino acids. The interaction between the agglutinin and egg-white lysozyme was not inhibited by chaotropic salts, but was sensitive to relatively low concentrations of urea. An affinity chromatographic procedure was developed in an effort to purify the agglutinin. Products from the chromatographic procedure were found not to contain higher specific agglutinating activities than the crude extract. Amino acid acid analyses of the extract showed the presence of relatively high proportions of glutamic and aspartic acids. In addition, the extract contained phosphorus and a visible chromophore. The agglutinin was resistant to detergents and denaturants, and proteases, nucleases, and other enzymes. The results suggest that, as opposed to other plant agglutinins, the active component from Persea is not a protein. Similarly, in contrast to many lectins, the agglutinin from Persea was not mitogenic for mouse lymphocytes. The agglutinin partially inhibited the mitogenesis of lymphocytes when the cells were treated with concanavalin A, or with bacterial lipopolysaccharide.