Table 1 The effect of HTLV-1 infection... | American Society of Hematology

Table 1

The effect of HTLV-1 infection on the frequency of T_regs depends on the phenotypic definition of T_regs

Patients	% FoxP3⁺ in CD4⁺ cells	% FoxP3⁺ in the CD4⁺CD25⁺ fraction
Uninfected 1	1.1	33.1
Uninfected 2	0.7	33.8
AC 1	1.2	22.6
AC 2	2.2	35.6
HAM/TSP 1	4.6	13.4
HAM/TSP 2	6.1	11
HAM/TSP 3	5.6	5
HAM/TSP 4	3.4	15.3

Patients	% FoxP3⁺ in CD4⁺ cells	% FoxP3⁺ in the CD4⁺CD25⁺ fraction
Uninfected 1	1.1	33.1
Uninfected 2	0.7	33.8
AC 1	1.2	22.6
AC 2	2.2	35.6
HAM/TSP 1	4.6	13.4
HAM/TSP 2	6.1	11
HAM/TSP 3	5.6	5
HAM/TSP 4	3.4	15.3

HTLV-1 infection was associated with an increase in the proportion of CD4⁺ T cells that express FoxP3 (column 1). This increase was especially marked in patients with HAM/TSP, who have a high proviral load of HTLV-1 and a high rate of proviral expression. However, the proportion of CD4⁺CD25⁺ cells that express FoxP3 was lower in patients with HAM/TSP than in uninfected individuals. The explanation for this is that HTLV-1 infection of CD4⁺ T cells strongly induces CD25 expression, thereby increasing the denominator of the fraction FoxP3⁺/CD4⁺CD25⁺. Because of the confounding effect of HTLV-1–induced expression of CD25, in the present study we avoided the use of CD25 in the working definition of the phenotype of T_regs, and used instead the simpler definition CD4⁺FoxP3⁺.

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