Actinomycin D:
Induction of surface antigen CD69 expression in
T-lymphocytes following exposure to actinomycin D.
Int J
Immunopharmacol 1999 Oct;21(10):689-703
Actinomycin D
Morgan CD, Greene JF Jr, Measel JW Jr.
Department of Pathology, Scott & White Hospital and Clinic, Scott, Sherwood
and Brindley Foundation, Texas A&M University System Health Science Center
College of Medicine, Temple, Texas, USA. cmorgan@swmail.sw.org
The expression of surface antigen CD69 in immune response cells is typically
associated with the early stage(s) of cell activation, with maximal expression
levels within 4 h of appropriate antigenic or mitogenic stimulation, and
maintenance of these high expression levels for 18-24 h. The expression
profiles of CD69 in human peripheral blood mononuclear cells (PBMC) cultured
with actinomycin D prior to mitogenic stimulation were evaluated by direct
immunofluorescence using flow cytometry. Pretreatment of PBMC suspensions with
low, non-toxic levels of actinomycin D stimulated CD3+ T-lymphocytes to
express CD69 in a concentration-dependent manner. Furthermore, CD4+
T-lymphocytes were the primary cells responding in this fashion. Secondary
mitogenic stimulation following antibiotic treatment potentiated cellular CD69
expression in these assays. CD69 expression was profoundly suppressed with in
vitro actinomycin D concentrations >/=1-2 microg/ml, presumably by
interference with cellular transcription/translation mechanisms. Parallel
thymidine incorporation assays indicated that actinomycin D effectively
inhibited thymidine uptake in a concentration-dependent manner, with complete
inhibition at >/=0.1 microg/ml. The evaluation of cell cycling dynamics
following antibiotic treatment, with and without secondary mitogen
stimulation, indicated no substantial changes in DNA synthesis over controls.
The diversity of these responses suggests that expression of CD69 may not
solely reflect mitogenic activation status but may, under some conditions,
result from induced cellular stress.
