IgA in secondary anti-hapten responses in vitro.

Production of IgA anti-hapten antibodies in vitro was studied in suspension and fragment cultures of spleens from mice immunized with NIP-CG (4-hydroxy-5-iodo-3-nitrophenylacetyl coupled to chicken globulin) a few weeks earlier. IgA anti-hapten production tended to be of much shorter duration than IgG anti-hapten production. IgA produced in fragment cultures had sedimentation coefficients of 9S, 11S, and 13S. 9S IgA anti-hapten was more prominent later during the in vitro response than earlier. In suspension cultures IgM anti-hapten production preceded IgA and IgG anti-hapten production. Very little IgM anti-hapten was seen in fragment cultures, although the responses on a cell-to-cell basis tended to be much higher in fragment than in suspension cultures.