Radioimmunoassay and immunochemistry of Phaseolus vulgaris phytohemagglutinin: verification of isolectin subunit structures

Toxicity Assessment of Common Beans (Phaseolus vulgaris L.) Widely Consumed by Tunisian Population

This research aimed at assessing the content and the functional properties of phytohemagglutinin (PHA) in different varieties of beans widely consumed in Tunisia through soaking, cooking, autoclaving, germination, and their combinations. This study was carried out on three varieties of white beans grown in different localities of Tunisia, namely Twila, Coco, and Beldia, as well as on imported and local canned beans. All bean samples underwent biochemical and immunological evaluation by employing several techniques such as indirect competitive enzyme-linked immunosorbent assay (ELISA), hemagglutinating assay, Ouchterlony double immunodiffusion, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Biochemical and immunological analyses indicated that raw dry beans contained a considerable amount of proteins and PHAs. ELISA demonstrated that soaking, either in plain water or in alkaline solution, caused an increase in the concentration of PHA. A slight increase of PHA was produced equally by germination during 4 days in all bean varieties. Cooking or autoclaving of presoaked beans resulted in a complete disappearance of PHA. ELISA test also proved that both imported and local canned beans contained fingerprints of PHA. Hemagglutination assays showed that not only cooked and autoclaved presoaked beans lacked the ability to agglutinate red blood cells but also autoclaved unsoaked beans did. In agar gel immunodiffusion using rabbit anti-PHA serum, raw, soaked, cooked unsoaked, and sprouted beans gave precipitin arc reactions, indicating that PHA existed in immunoreactive form in the tested seeds. SDS-PAGE electrophoretograms showed protein isolates of Twila and Beldia beans to have different profiles through soaking, cooking, and autoclaving processes. This work revealed that the combination of soaking and cooking/autoclaving was the best way in reducing PHA content and its activity in all bean varieties when compared with germination.

Mitogenic and mitogenically defective phytohemagglutinin isolectins stimulate T-cell growth factor (interleukin 2) production and response in fresh and cultured human T lymphocytes

L4-PHA (L4) and E4-PHA (E4) lectins isolated from Phaseolus vulgaris have different mitogenic properties. The mechanisms of the differences in mitogenic behavior were sought in the interaction of lectin, lymphocyte subsets, and T-cell growt factor (TCGF) also known as interleukin 2 (IL-2). TCGF activity in culture supernatants ( L4S ; E4S ) from L4- and E4-stimulated, freshly isolated lymphocytes was assayed as stimulation of DNA synthesis in TCGF-dependent continuous T-cell cultures (CTC). E4S contained less TCGF than did L4S . Addition of partially purified TCGF does not increase the stimulation of fresh lymphocytes by L4 or E4. L4 and E4 equally stimulate both helper (OKT4+) and suppressor (OKT8+) cells. The ability of L4 to further stimulate CTC is slowly lost (15 greater than 30 greater than 45 days). It is concluded that production of TCGF is not rate limiting in E4 and L4 stimulation of lymphocytes. The growth of CTC, which requires the presence of TCGF, remains sensitive to, but not dependent on, L4 for at least 30 days.