Abnormal activation and cytokine spectra in lymph nodes of people chronically infected with HIV-1

Abstract

There is growing recognition that HIV-1 infection leads to an activation of the immune system that includes perturbations of cytokine expression, redistribution of lymphocyte subpopulations, cell dysfunction, and cell death. Here, we explored the relationships between HIV-1 infection and immune activation in chronically HIV-1-infected human lymph nodes. In addition to CD4 T-cell depletion, we found increased effector T-cell frequencies associated with profound up-regulation of an activation marker CD38 in naive, central memory, and effector CD4(+) and CD8(+) T cells. Likewise, Fas death receptor (CD95) was more frequently detectable on T cells from HIV-1 nodes. Dendritic cell (DC) depletion was dramatic, with plasmacytoid DCs (PDCs) 40-fold and myeloid DCs (MDCs) 20-fold less frequent in HIV(+) nodes than in control nodes. Cytokine dysregulation was evident, with IL-2 and IL-15 as much as 2 or 3 logs greater in infected nodes than in control nodes. Thus, activated effector cells are inappropriately attracted and/or retained in lymphoid tissue in chronic HIV-1 infection. High-level cytokine expression in turn activates and retains more cells at these sites, leading to lymphadenopathy and massive bystander activation that characterizes HIV-1 infection. Strategies targeting these activation pathways may lead to new therapies.

Figure 1

Lymphocytes of various immunotypes in lymph nodes of patients chronically infected with HIV-1 and patients without HIV-1. Phenotype of cells was characterized by flow cytometry after staining with specific antibodies against surface markers at day 1 after surgery. The numbers shown are the percentage of viable T cells. **P < .05 as evaluated by nonparametric Mann-Whitney test. (A) Distribution of lymph node lymphocytes. Boxes represent the 25th-75th percentile of data; medians are indicated, and bars represent the data range of patients with chronic HIV-1 (n = 10; ■) and patients without HIV-1 (n = 10; □). (B) Ratio of CD4/CD8 lymphocytes. Boxes represent the 25th-75th percentile of data; medians are indicated, and bars indicate the data ranges of the ratio for lymph nodes from 10 chronically infected (left panel) and 10 uninfected (right panel) individuals. For each donor tissue, the number of CD4 and CD8 T cells was measured in 3 pooled tissue blocks and uninfected control.

Figure 2

Subpopulation of naive and memory CD4 and CD8 T cells in lymph nodes of patients with chronic HIV-1 and patients without HIV-1. Cells were phenotyped by flow cytometry at day 1 after surgery. Presented are the mean numbers of living T cells expressing CD4 (A-B) or CD8 (C-D) in lymph nodes from infected (A and C) or uninfected (B and D) individuals. The results represent means of the data obtained with sets of 3 tissue blocks derived from 8 donors with HIV-1 and 5 patients without HIV-1. ■ indicates the mean for central memory T cells; ▩, the mean for naive T cells; and □, effector T cells. *P < .05 for the difference between chronic HIV-1–infected and uninfected control tissue as evaluated by nonparametric Mann-Whitney test. (A) CD4 T lymphocytes subpopulation in chronic HIV-1–infected lymph nodes. (B) CD8 T lymphocyte subpopulation in chronic HIV-1–infected lymph nodes. (C) CD4 T lymphocyte subpopulation in uninfected control lymph nodes. (D) CD8 T lymphocyte subpopulation in uninfected control lymph nodes.

Figure 3

Activation status memory/naive subtypes among CD4 and CD8 T cells in lymph nodes from patients with chronic HIV-1 and patients without HIV-1. Cells were stained for lineage markers, activation (CD38), and memory/naive markers expression on day 1 after surgery. (A-B) Medians (25th-75th percentile) for data obtained with sets of 3 tissue blocks derived from each of 8 patients with chronic HIV-1 and 5 patients without HIV-1. (A) Percentage of cells expressing CD38 among total, naive, effector memory, and central memory CD4 lymphocytes. (B) Percentage of cells expressing CD38 among total, naive, effector memory, and central memory CD8 lymphocytes. Fraction of total T cells expressing CD38 correlated to clinical data from patient CD4 cell count (C) and plasmatic viral load (D). (C) Correlation between the fraction of T cells expressing CD38 at day 1 and the number CD4 T cells. (D) Correlation between the fraction of T cells expressing CD38 at day 1 and the plasmatic viral load. Lines represent linear regressions.

Figure 4

PDCs and MDCs in lymph nodes from patients with chronic HIV-1 and patients without HIV-1. Phenotype of cells was characterized by flow cytometry after staining with specific antibodies against surface markers. DCs are defined as viable Lin⁻ HLA-DR⁺ cells expressing particular surface markers CD123 for PDCs and CD11c for MDCs. (A) Flow cytometry of PDCs and MDCs in lymph nodes. Dot-plot of cells lymph nodes from representative patients with chronic HIV-1 (left panel) and patients without HIV-1 (right panel). (B) Number of PDCs and MDCs in lymph nodes in 3 different donors. Presented are values of the cell numbers expressed as percentages of Lin⁻ HLA-DR⁺ cells for sets of 3 tissue blocks derived from each of 3 patients with chronic HIV-1 and 4 patients without HIV-1.

Figure 5

Chemokines and cytokines in lymph nodes of patients with chronic HIV-1 and patients without HIV-1. Presented are concentrations of chemokines/cytokines released by uninfected and HIV-1–infected lymph nodes (6 or fewer blocks number 27 or less in 3 mL of medium) over 15 days in culture. Black symbols indicate chronic HIV-1–infected lymph nodes; gray symbols, normal lymph nodes. For HIV-1–infected lymph nodes, each square represents data from 1 of 10 donors. For uninfected lymph nodes, each triangle represents data from 1 of 10 donors. Line denotes median of the concentrations for each cytokine. *Statistical significance for a nonparametric Mann-Whitney test performed on the median of concentrations (P < .05).