Toxin production by strains of Aeromonas hydrophila grown in laboratory media and prawn purée.

Toxin production by four strains of Aeromonas hydrophila grown at 30 and 37 degrees C in two laboratory media and prawn purée was studied. Three different cell lines were used to test for cytotoxic activity, haemolytic activity was tested against rabbit and guinea pig erythrocytes, proteolytic activity was assayed with azo-casein and enterotoxic activity using the suckling mouse assay. Results showed reduced cytotoxic and haemolytic activities in prawn purée compared with the two media, but in most cases increased proteolytic activity. No enterotoxic activity was observed in prawn purée although it was occasionally detectable in both laboratory media.

The species distribution of three concanavalin A-purified mycobacterial polysaccharides.

Culture filtrates prepared from 12 species of mycobacteria were examined for the presence of 3 mycobacterial polysaccharides previously purified by concanavalin A affinity chromatography. Four commercial Old Tuberculins, tuberculin tine test units, and purified protein derivative were also studied. All 3 polysaccharides were demonstrated in all of the filtrates and each of the Old Tuberculins and purified protein derivative. The amount of concanavalin A-nonreactive polysaccharide was measured in clinical skin testing antigens and found to be in the range of potential significance as a cause of false positive reactions to Old Tuberculin.

Accessory cell function of rabbit alveolar macrophages.

Alveolar macrophages (AM) are the first cells to contact inhaled antigen. Accessory cell function of AM would modulate the immunologic response to antigenic exposure. We sought to examine the capability of AM to act as accessory cells for proliferation of lymphocytes using conditions that are best suited for expression of this function. We used rabbit popliteal lymph node cells, both before and after depletion of macrophages by 2 successive Sephadex G-10 columns that decreased nonspecific esterase positive cells from 2.56 to < 0.1%, and abolished or markedly decreased concanavalin A-induced lymphocyte proliferation. AM were lavaged from rabbit lungs and treated with mitomycin C. We found that AM enhanced proliferation of 5 x 10(4) and 7 x 10(4) unseparated, lymph node cells 5- to 15-fold, but had no effect on 2 x 10(5) cells. The optimal ratio of macrophages to lymphocytes (AM:L) was between 1:2 and 2:1. An AM:L value of 4:1 suppressed proliferation. The addition of AM to macrophage-depleted lymph node cells enhanced proliferation of 5 x 10(4), 7 x 10(4), and 2 x 10(5) lymphocytes 15- to 50-fold (AM:L, 1:2 to 2:1). Excessive numbers of macrophages (AM:L, 4:1) suppressed proliferation 5- to 50-fold. Rabbit AM can act as accessory cells in assays of mitogen-induced lymphocyte proliferation with maximal effect at AM:L values of 1:2 to 2:1. Suppression can occur as a result of excessive numbers of macrophages.

Assessment of an enzyme immunoassay for the detection of salmonellas in foods and animal feeding stuffs.

The Salmonella Bio-EnzaBead Screening Kit, in its modified form with both the MOPC 467 and the 6H4 antibodies, was used for the detection of salmonellas in naturally contaminated foods and animal feeding stuffs in parallel with a traditional cultural procedure. Initial results showed an 82% agreement between the enzyme immunoassay (EIA) and cultural methods when using the criterion recommended by the manufacturer as a cut-off for all types of foods. By adjusting the cut-off for each type of food, the number of EIA positive, culture negative samples was reduced although the number of EIA negative, culture positive samples increased. The EIA may be more sensitive than the cultural methods as in many cases the EIA positive, culture negative results could be real positives which were not detected by the cultural methods. The screening kit provides a simple and convenient method for the detection of salmonella in foods and feeds and a presumptive positive result can be reported within 48 h. The advantages and disadvantages of the method are discussed.

Immunobiology and species distribution of Mycobacterium tuberculosis antigen 5.

The immunobiology and mycobacterial species distribution of immunoabsorbent affinity chromatography-purified Mycobacterium tuberculosis antigen 5 have been studied. In delayed hypersensitivity skin tests, antigen 5 was nearly equipotent with tuberculin-purified protein derivative in sensitized guinea pigs. In vitro, antigen 5 was capable of stimulating the production of migration inhibitory factor by cultured lymphocytes from sensitized guinea pigs and humans. Antigen 5 stimulated thymidine incorporation by cultured guinea pig lymphocytes but did not stimulate thymidine incorporation by cultured human lymphocytes. Although erythrocytes were readily sensitized with antigen 5 for passive hemagglutination, their use did not offer any advantage over previous hemagglutination techniques for the serodiagnosis or evaluation of patients with tuberculosis. By immunoelectrophoresis and immunodiffusion, antigen 5 was readily identified in culture filtrates of 10 strains of M. tuberculosis and M. bovis but not in those of 30 strains of 12 other myobacterial species.