6th ESACP Congress, Heidelberg, April 7-11, 1999

A017
CYTOMETRIC ANALYSIS OF IMMUNOLOGICAL MEMORY
Radbruch A, Assenmacher M *, Broisterhus H *, Löhning M, Leyendeckers H *, Miltenyi S *, Nitsch S, Richter A, Scheffold A, Schmitz J *, Thiel A

Deutsches Rheumaforschungszentrum, Berlin, and * Miltenyi Biotech, Bergisch-Gladbach

Memory for antigens encountered previously in life is one of the most intriguing characteristics of the immune system. Despite their relevance for immunopathology, the cells that confer it, their molecular setup and their differentiation are still not well characterized. For cytometric approaches, the low frequencies of cells memorizing particular antigens and the transient and secretory expression of important molecules of immune reactions, chemokines, cytokines and antibodies, have hindered the cytometric analysis, cell sorting and functional and molecular characterization of memory lymphocytes. In the recent past we have developed a series of new cytometric technologies, allowing us to label viable cells according to secreted products and rare surface molecules, and to isolate them efficiently, even if they are extremely rare. We have used these techniques to identify the long lived plasma cell as the cell responsible for humoral memory, i.e. long lasting protective serum antibody titers. Their generation is controlled by T lymphocytes via cytokines. The T cell memory for expression of particular cytokines is essential for the generation of new plasma cells from memory B lymphocytes, and of cytotoxic T lymphocytes from their precursors. Complex patterns of cytokines expressed by individual cells control the kind of immune reaction and by this, whether protection or immunopathology is achieved. Cytokine cytometry and the isolation of viable cells according to cytokine expression has contributed significantly to reveal the molecular basis of cytokine memory and offers options to manipulate it, in immunopathology, autoimmunity and allergy, and for the development of vaccination strategies.