Abstracts (complete list) - Wissenschaft Online

Inga Gebuhr, Kathrin Gube, Katrin Vogt, Christian Meisel, Sandra Naundorf, Hans-
Dieter Volk, Birgit Sawitzki
Importance of cell surface N-glycosylation for activation of T
cell subpopulations
Introduction: Recently, we demonstrated that infiltrating CD4+ T cells of tolerance
developing kidney grafts recipients express high levels of alpha-1,2-Mannosidase, an
important enzyme for the N-glycosylation of proteins. The impact of N-glycosylation of
surface proteins such as costimulatory molecules on T cells for their activation is still
poorly understood.
Aim: Here we investigated the role of alpha-1,2-Mannosidase and cell surface Nglycosylation
for the activation of different T cell subpopulations.
Methods: Human CD4+, CD4+CD45RA naïve, and CD4+CD45RO memory T cells were
purified using MACS separation. Cells were cultivated for 2 days in the presence or
absence of the alpha-1,2-Mannosidase specific inhibitor Kifunensine. Preincubated T
cells were stimulated with allogenic PBMCs. PHA binding was used to determine
Mannosidase activity. CD69 expression, cytokine production and Mannosidase
transcription was analysed.
Results: The inhibition of Mannosidase activity in CD4+ T cells prior to stimulation
resulted in a dramatic reduction of cell surface N-glycosylation levels. This reduction
was accompanied by 2 to 3 fold increase in CD69 frequency, an earlier IL-2 production
and transcription. This early increase in IL-2 production was due to faster activation of
ERK. Interestingly, memory T cells displayed 5 fold higher transcription levels and 2 fold
increased PHA binding capacities when compared to naïve T cells. During allostimulation
mRNA transcription in memory T cells did not change whereas in naïve T
cells transcription was transiently down-regulated followed by a 4 fold upregulation.
Furthermore, naïve and memory T cells also differ in their susceptibility to Nglycosylation
mediated regulation of T cell activation. Only in naïve T cell inhibition of Nglycosylation
resulted in increased cytokine production.
Conclusions: Our data show that N-glycosylation of cell surface proteins negatively
regulates T cell activation. Furthermore the magnitude and impact of N-glycosylation is
highly regulated among T cell subpopulations.