Differences in the frequency of cytokine-producing cells in antigenemic and nonantigenemic individuals with bancroftian filariasis

Abstract

Individuals with clinical manifestations of lymphatic filariasis may be currently infected or not. Twenty-five individuals from a Wuchereria bancrofti-endemic area of Brazil were classified as being asymptomatic microfilaremic individuals, antigenemic individuals with clinical filariasis, or nonantigenemic individuals with clinical filariasis. Intracellular cytokine staining of mitogen-stimulated peripheral blood mononuclear cells (PBMC) showed that the frequency of either gamma interferon (IFN-gamma)- or interleukin-4 (IL-4)-producing cells was higher in the nonantigenemic individuals with clinical filariasis than in the asymptomatic microfilaremic individuals (geometric means, 22.1 versus 10.7% [P = 0.02] and 2.9 versus 1.4% [P = 0.01], respectively). When the asymptomatic microfilaremic individuals and antigenemic individuals with clinical filariasis were grouped together to constitute all actively infected individuals, the frequency of IFN-gamma-producing cells was also lower than in the nonantigenemic individuals with clinical filariasis (P = 0.04). Likewise, the frequency of IL-4-producing cells in the actively infected individuals was also lower than in the nonantigenemic individuals with clinical filariasis (P = 0.02). No differences in the frequency of IFN-gamma-, IL-4-, or IL-5-producing cells in purified CD4 T lymphocytes were found among the groups. These findings suggest that the presence of antigenemia, which is an indicator of current active infection, is closely associated with the frequency of IFN-gamma- and IL-4-producing cells in lymphatic filariasis. The differences found in the frequency of cytokine-producing cells among the three groups appear to be due to a subset of cells other than CD4 T cells.

FIG. 1

Representative two-parameter dot plots of IFN-γ-, IL-4-, and IL-5-producing cells from medium- or PMA-ionomycin-stimulated cultures of PBMC. A and D, medium stimulation of PBMC from a nonantigenemic individual with clinical filariasis; B and E, mitogen stimulation of PBMC from an asymptomatic microfilaremic individual; C and F, mitogen stimulation of PBMC from a nonantigenemic individual with clinical filariasis. Quadrant statistics were set on the basis of the corresponding medium-stimulated cultures.

FIG. 2

Percentages of IFN-γ (A)-, IL-4 (B)-, and IL-5 (C)-producing cells in PMA-ionomycin-stimulated PBMC from asymptomatic microfilaremic individuals (MF), antigenemic individuals with clinical filariasis (Dis+ CAg+), nonantigenemic individuals with clinical filariasis (Dis+ CAg−), and normal control individuals (NC). Box plots display the 25th, 50th, and 75th percentiles of the cytokine responses. Percentage of IFN-γ-producing cells in all patient groups is the average of results from two separate samples. ∗, P < 0.05 compared to the Dis+ CAg− group; ∗∗, P < 0.05 compared to the actively infected group taken together (MF and Dis+ CAg+); ∗∗∗, P < 0.05 compared to the MF, Dis+ CAg−, or actively infected group.

FIG. 3

Percentages of IFN-γ (A)-, IL-4 (B)-, and IL-5 (C)-producing cells in PMA-ionomycin-stimulated CD4 T cells from asymptomatic microfilaremic individuals (MF), antigenemic individuals with clinical filariasis (Dis+ CAg+), nonantigenemic individuals with clinical filariasis (Dis+ CAg−), and normal control individuals (NC). Box plots display the 25th, 50th, and 75th percentiles of the cytokine responses. Percentage of IFN-γ-producing cells in all patient groups is the average of results from two separate samples.

FIG. 4

Correlation of frequency of IFN-γ (A)-, IL-4 (B)-, and IL-5 (C)-producing cells with the levels of secreted cytokine in culture supernatants from PMA-ionomycin-stimulated CD4 T cells of subjects in the three patient groups. Correlations are a result of linear regression analysis.