Blood, 1 September 2001, Vol. 98, No. 5, pp. 1506-1511
IMMUNOBIOLOGY
In vitro spontaneous lymphoproliferation in patients with human
T-cell lymphotropic virus type I-associated neurologic disease:
predominant expansion of CD8+ T cells
Jill A. Sakai,
Masahiro Nagai,
Meghan B. Brennan,
Carlos A. Mora, and
Steven Jacobson
From the Viral Immunology Section, Neuroimmunology
Branch, National Institute of Neurological Disorders and Stroke,
National Institutes of Health, Bethesda, MD.
Peripheral blood mononuclear cells (PBMCs) from patients with
human T-cell lymphotropic virus type I (HTLV-I)-associated
myelopathy/tropical spastic paraparesis (HAM/TSP) proliferate
spontaneously in vitro. This spontaneous lymphoproliferation (SP)
is one of the immunologic hallmarks of HAM/TSP and is considered to be
an important factor related to the pathogenesis of HAM/TSP. However,
the cell populations involved in this phenomenon have not yet been
definitively identified. To address this issue, the study directly
evaluated proliferating cell subsets in SP with a flow cytometric
method using bromodeoxyuridine and Ki-67. Although both
CD4+ and CD8+ T cells proliferated
spontaneously, the percentage of proliferating CD8+ T cells
was 2 to 5 times higher than that of CD4+ T cells. In
addition, more than 40% of HTLV-I Tax11-19-specific CD8+
T cells as detected by an HLA-A*0201/Tax11-19 tetramer proliferated in
culture. In spite of this expansion of HTLV-I-specific
CD8+ T cells, HTLV-I proviral load did not decrease. This
finding will help elucidate the dynamics of in vivo virus-host
immunologic interactions that permit the coexistence of high
HTLV-I-specific CD8+ cytotoxic T-lymphocyte responses and
high HTLV-I proviral load in HAM/TSP.
