Distribution of Monoclonal Antibodies in Intestinal and Urogenital Secretions of Mice Bearing Hybridoma ‘Backpack’ Tumours

Mice bearing IgA hybridoma ‘backpack’ tumours have been used to demonstrate that secretion of a single monoclonal IgA can protect against mucosal infection, but the relevance of this model to normal IgA protection is not clear. The authors analysed the distribution of specific monoclonal and total antibodies in bile, local intestinal secretions, cervical‐vaginal secretions, urine and serum of mice bearing anti‐cholera toxin (CT) IgA and IgG backpack tumours, with and without bile duct ligation. Backpack tumours resulted in high levels of both anti‐CT and total IgA or IgG in serum, and IgA (but not IgG) in bile. Secretions recovered by absorbent filter ‘wicks’ from mucosal surfaces throughout the intestines of backpack tumour mice contained significant concentrations of monoclonal anti‐CT IgA, but total IgA levels were as in normal mice. Neither monoclonal nor total IgA levels on mucosal surfaces were altered by bile duct ligation. Furthermore, anti‐CT monoclonal IgA levels in local intestinal secretions of backpack tumour mice were comparable to specific polyclonal IgA levels previously elicited by mucosal immunization with CT. Thus, IgA‐mediated protection against enteric challenge in the backpack tumour model may be a valid predictor of protection provided by natural mucosal immunization in vivo . High monoclonal IgA levels in bile, urine and the female genital tract, however, may not reflect the situation in normal immunized mice.