Mouse ear spleen grafts: a model for intrasplenic immunization with minute amounts of antigen.

The production of monoclonal antibodies to protein antigens which can only be obtained in tiny amounts has been a major task, since classical in vivo immunization procedures are not always efficient. In order to circumvent this problem, two methods have been developed: (1) in vitro immunization, in which the immunogen is presented directly to spleen cell cultures; (2) intrasplenic immunization, a technique in which the immunogen is deposited in the spleen tissue. The latter approach requires less laboratory work and the risk of contamination, often a problem with in vitro cultures (Nilsson and Larsson, Immunol. Today (1990) 11, 10), is greatly reduced. Here, we describe a novel method of grafting neonatal spleens in the pinna of the mouse ear. Histological and functional studies show that these spleen grafts have white and red pulp and contain normal percentages of functional T and B cells. The results indicate that this procedure is extremely efficient in priming mice for a secondary humoral immune response, since very small amounts of soluble antigen (ovalbumin) were required. The data are discussed in terms of the advantages of this new technique over current procedures for intrasplenic immunization.