Lymphoid tissues cultured either as tissue blocks or as cell suspensions are used to study the behaviour of immune cells within their habitat. The preservation of tissue structures in tissue blocks, which is considered to be a major advantage, has been poorly defined. We characterised the morphological evolution of tissue cultures from human palatine tonsils and compared their lymphocyte subsets and the constitutive cytokine gene expression to those in autologous tonsillar single-cell suspension cultures over time, and after adding cyclosporin A (CsA) to mimic the situation in individuals treated with immunosuppressive drugs. Density and morphology of follicles were conserved up to 4 days, during which tissue cultures exhibited similar cell viability as suspension cultures, but a significantly less frequent increase of CD95 expression in T cells, smaller variation of the proportion of CD4(+) cells and better CD21(+)/CD23(-) B-cell survival. Treatment with cyclosporin A at higher concentrations resulted in superior histologic preservation of lymphoid tissue structures and seemed to further prevent the expression of CD95 by CD3(+) cells and the activation in tissue culture of CD21(+) cells. Constitutive gene expression levels of the stromal cytokines interleukin (IL)-1beta and interleukin-6 in tissue culture were significantly higher than those in suspension cultures. These results suggest that tonsillar tissue cultures preserve their structure only for a limited time, during which they more closely reflect processes in vivo, including a state of iatrogenic immunosuppression, than do their cell suspension counterparts.