Abstracts (complete list) - Wissenschaft Online

Timo Lischke, Andreas Hutloff, Richard A. Kroczek
ANALYSIS OF CD4+ T CELL IMMUNITY IN VIVO
We intend to study the development of CD4+ T cell memory in vivo. In a first step,
many of the in vitro data on the expression of cell surface communication molecules
have to be re-derived from in vivo experiments. To establish a baseline for future
experiments aimed at defining the influence of inflammatory agents on the development
of CD4+ T cell memory, we have adoptively transferred transgenic, ovalbumin (OVA)specific
CD4+ T cells into syngeneic murine recipients, which were subcutaneously
immunized with OVA + lipopolysaccharide. The draining lymph nodes were removed at
defined time points and the OVA-specific CD4+ T cells were analysed for the expression
of activation markers such as CD69 and CD25, and for the expression of the
costimulatory molecules 4-1BB, OX40, ICOS, PD-1, and BTLA. CD69 and CD25 became
detectable already 6 h after immunization on most OVA-specific CD4+ T cells; 4-1BB
was hardly expressed at all. Expression of OX40 and ICOS could be seen at 12 h, with
maxima at 24 h and 48 h, respectively. The kinetics for PD-1 and BTLA, the negative
regulators of T cell activation, were more extended. Further, we determined the exact
expansion and contraction kinetics of CD4+ T cells using CSFE labelling. In the late
phase of the immune response (days 5 – 21), we recorded the development of OVA
specific CD4+ CD44+ CD62L− effector-memory and CD44+ CD62L+ central-memory T
cells, but did not observe the appearance of FoxP3+ regulatory T cells. The degree of T-
B interaction was assessed by measuring the serum levels of OVA-specific IgG1, IgG2a,
and IgG2b. This comprehensive analysis of the CD4+ T cell response will be
instrumental for the future dissection of the decision points for memory formation in
vivo.