Leukocytes, or white blood cells, are used for a variety of investigational purposes and they offer advantages over laboratory-adapted cell lines. Leukocytes that are typically discarded by blood banks during the collection of red blood cells, platelets, and plasma can often be obtained for research use. However, the available leukocytes are frequently contained within a blood filtration device, such as the Terumo LR Express (TLRE) filter. In this study, procedures were evaluated for the ability to elute viable leukocytes from TLRE filters. The recovered leukocytes were assessed for composition, growth, and functionality. The large majority (>70%) of leukocytes were eluted with a single reverse-elution procedure and the recovered cells contained representative populations of the major leukocyte subsets. Purified T cells exhibited diverse T cell receptor repertoires, characteristic growth upon mitogen stimulation, and CD4+ T cells were able to support HIV-1 propagation. Purified monocytes were able to be differentiated into phenotypically characteristic populations of macrophages and dendritic cells. Overall, TLRE filters offer an attractive source of primary human cells for research and possibly clinical purposes.

The adaptive immune response to viral infections features the antigen-driven expansion of CD8+ T cells. These cells are widely recognized for their cytolytic activity that is mediated through the secretion of cytokines such as perforin and granzymes. Less appreciated is their ability to secrete soluble factors that restrict virus replication without killing the infected cells. In this study we measured the ability of primary anti-CD3/28-stimulated CD8+ T cells from healthy blood donors to secrete interferon-alpha. Supernatants collected from CD8+ T cell cultures were screened for their ability to suppress HIV-1 replication in vitro and their interferon-alpha concentrations were measured by ELISA. Interferon-alpha concentrations in the CD8+ T cell culture supernatants ranged from undetectable to 28.6 pg/mL. The anti-HIV-1 activity of the cell culture supernatants was observed to be dependent on the presence of interferon-alpha. Appreciable increases in the expression levels of type 1 interferon transcripts were observed following T cell receptor stimulation, suggesting that the secretion of interferon-alpha by CD8+ T cells is an antigen-driven response. In 42-plex cytokine assays, the cultures containing interferon-alpha were also found to contain elevated levels of GM-CSF, IL-10, IL-13, and TNF-alpha. Together, these results demonstrate that the secretion of anti-viral levels of interferon-alpha is a common function of CD8+ T cells. Furthermore, this CD8+ T cell function likely plays broader roles in health and disease.

Background CD8+ T cells play important roles in the antiviral immune response to HIV-1 infection. Variation in the antiviral activities of CD8+ T cells among HIV-1-infected persons has been associated with disease state and clinical prognosis. However, the anti-HIV activities of CD8+ T cells from healthy uninfected blood donors have not been fully established. Methods In this study we assessed the ability of peripheral blood CD8+ T cells from healthy blood bank donors to inhibit HIV-1-replication. Co-culture assays were performed with CD8+ T cells and acutely HIV-1-infected primary CD4+ T cells. Also, CD8+ T cells were cultured and the derivative supernatants were evaluated in virus inhibition assays, ELISAs, and multiplex cytokine arrays. Results Variation was observed among CD8+ T cells from different blood donors in the ability to suppress HIV-1 replication. In the absence of stimulation, the CD8+ T cells, or their derivative fluids, lacked any appreciable anti-HIV activity. After PHA or anti-CD3/CD28 stimulation, the majority of CD8+ T cells and derivative fluids exhibited anti-HIV activity. Low levels of interferon-alpha were present in the CD8+ T cell fluids having increased anti-HIV activity, whereas CD8+ T cell fluids lacking anti-HIV activity contained undetectable levels of interferon-alpha. Other soluble factors present at increased levels in CD8+ T cell fluids having anti-HIV activity included TNF-beta, IL-8, IP-10, and TRAIL. Conclusions Our findings indicate that the secretion of antiviral levels of interferon-alpha is a normal function of CD8+ T cells in response to activation and stimulation. Variation in this immune response may influence host susceptibility to infection and disease.