A comparison of the performance in vitro of precision cut tissue slices and suspensions of human spleen with special reference to immunoglobulin and cytokine production

During the past decade our knowledge of the cellular and molecular events associated with key immunological responses has been greatly advanced by the use of isolated subpopulations of immunocompetent cells, cloned cell lines and recombinant derived cytokines. Valuable as these studies have been they do not truly reflect the complex integrative events which take place in both primary and secondary lymphoid tissue both in vivo and in vitro. In order to address this problem we have developed a tissue culture procedure which is a modification of that previously used by others to study T cell maturation in the thymus. This involves culturing precision cut slices of human lymphoid tissue in a sponge culture system. Using this technique we have observed marked differences in both immunoglobulin and cytokine secretion between slices and suspensions of human spleen. In brief cultured slices (mitogen stimulated or otherwise) consistently secrete higher levels of immunoglobulin, IL-1β, IL-6, IL-8 and IL-11 and exhibit much lower proliferation than suspensions of the same tissue. Mitogen stimulated suspensions on the other hand secrete higher levels of IL-2, IL-4, IL-10 and TNFα than do slices. These differences are also observed at the intracellular cytokine level. Additional studies reveal that the immunoglobulin and cytokine secretion observed is largely due to the de novo synthesis of these molecules and not as a result of spontaneous secretion of preformed products. Furthermore immunoglobulin secretion in both slices and suspensions can be inhibited by the addition of specific antibodies to IL-1β, IL-6 and TNFα while IL-6 production can be differentially modulated by a variety of substances. Preliminary studies indicate that close interaction between B cells and stromal cells within ex plants accounts for some of the observed differences. This review article describes the basic technique, summarises the results we have obtained in this system and outlines the possible basis of the observed differences.