72
ICCS 2011
P36
The utility of CD200 and CD23 expression in
chronic lymphocytic leukaemia (CLL) and mantle
cell lymphoma (MCL)
Sue Wong, Mary Sartor, Zarah Timbol, Ken
Bradstock, David Fulcher
Flow cytometry unit, ICPMR, Westmead Hospital,
Westmead, Australia
CD200 (OX-2 antigen) is a type 1 transmembrane
immunoglobulin (Ig) superfamily glycoprotein that
is expressed on normal B- and T-cells, dendritic,
endothelial and neuronal cells. In mice, the binding
of CD200 to its receptor, CD200R1, expressed by
myeloid-derived antigen-presenting cells and subsets
of T cells, promotes a suppressive effect on T-cell
responses. CD200 is highly expressed on clonal
cells in CLL, plasma cell myeloma and hairy cell
leukaemia, and its expression has been linked to
a poorer prognosis, consistent with the suggestion
that CD200 has a protective survival effect on
CLL cells. Based on these fndings, a humanised
monoclonal antibody against CD200 is available
as an anti-tumour treatment. For the purposes of
immunophenotyping, the distinction between CLL and
MCL, both CD5-positive lymphoproliferative disorders,
typically rests on CD23 expression, usually absent
in MCL but expressed by CLL cells. However in
atypical cases of CLL, CD23 may be negative. Since
CD200 expression is also reported to be absent in
MCL, we examined its utility in distinguishing these
disorders in a routine diagnostic laboratory. We will
present our detailed analysis of this study, although
preliminary data suggests that some cases of CLL
may be CD200-negative. As anti-CD200 therapy
becomes more common in the treatment for CLL as
well as other B-cell lymphoproliferative disorders,
determining the expression patterns for CD200 may
have important implications for treatment strategies
and minimal residual disease monitoring.
POSTER ABSTRACTS