The Potent lgG4-lnducing Antigen in Banana Is a Mannose-Binding Lectin, <i>BanLec-</i><i>I</i>

Abstract

IgG4 antibodies to banana were found to occur far more frequently than expected. The most important antigen involved proved to be a lectin, BanLec-I. Because of the lectin nature of the antigen, it was important to establish the antibody nature of the lectin-IgG4 interaction and to exclude an interaction between the sugar-binding site of the lectin and glycosidic chains on IgG4. Three arguments in support of immune binding are: (1) the binding of BanLec-I to IgG4 is mannoside resistant, whereas the binding to all other glycoproteins tested is mannoside inhibitable; (2) only a minor fraction of the IgG4 in serum and none of five IgG4 myelomas tested was bound, and (3) the lectin binds to the Fab fragment of the IgG4 molecule. A curious finding was that in the presence of high-molecular-weight glycoproteins the interaction between IgG4 and BanLec-I was enhanced by α-methyl mannoside. The probable explanation of this phenomenon is that complexes of the lectin with high-molecular-weight glycoproteins by sterical interference inhibit the interaction with human IgG4 antibodies (or with rabbit antibodies to the lectin). This inhibition is prevented in the presence of α-methyl mannoside. These results support the earlier suggestion that some lectins are particularly prone to induce an immune response upon oral feeding. This banana lectin might be a potentially useful carrier protein for oral antihapten immunization in humans.

Fruit-specific lectins from banana and plantain

“…Consequently, eating bananas can in principle lead to an immune response. The latter assumption is supported by the earlier observation that IgG4 antibodies against banana lectin are found with an unexpectedly high frequency in human serum (Koshte et al 1992). Though the eects of orally ingested banana lectin on humans are not necessarily negative, it is important to realize that this major fruit crop contains relatively high concentrations of a mannose-speci®c lectin.…”

The Abundant Class III Chitinase Homolog in Young Developing Banana Fruits Behaves as a Transient Vegetative Storage Protein and Most Probably Serves as an Important Supply of Amino Acids for the Synthesis of Ripening-Associated Proteins

“…Besides class I chitinases, sev-eral other banana pulp proteins like BanGase (Breiteneder and Scheiner, 1998;Yagami, 1998) and BanTLP (Breiteneder and Ebner, 2000) are considered possible allergens. In addition, BanLec, which was shown to induce the production of IgG4 antibodies upon oral uptake (Koshte et al, 1992) is suspected to cause the development of allergic symptoms by susceptible individuals. According to the results shown in Figure 4, ethephon-treated ex planta-ripening bananas accumulate less BanChi and BanTLP, which are the most potent allergens of the pulp, than untreated fruits.…”

Integrated Defense System Overlaps as a Disease Model: With Examples for Multiple Chemical Sensitivity

“…Other chemicals that induce autoimmune disturbances include halothane (184) and acetaldehyde (183), and biomarkers and symptoms in such disturbances exhibit variable data in multiple organs (197), indicating that several effects on the IRA may be occurring. In addition, food lectins such as BanLec 1 (found in bananas) can be inciters of IgG; lectins also interfere with the complement NIR (162,199,200), commonly act as superantigens (54,162), and are endocytosed in relatively large quantities in the gut (200).…”

“…In our model we assume that chronic exposure to vinyl chloride has damaged both IgG and other tissues and the IRA produces T-cell-mediated autoimmune complexes raised against these tissues (196). We do not know with certainty the memory mechanism of such autoimmune disturbances; possibly it involves DNA encoding in the variable (diversity) joining recombination of T cells (26,28,201,202 (199). Soy (204), beef (205), and corn (206) also induce IgG, as do various chemicals (181,182,206).…”