Lymphocyte Subsets (BCS, PCS1)
Two of the cold studies, BCS and PCS1, included assessment of lymphocyte subsets in baseline blood samples, thus providing a quantitative measure of basal immunity. Both studies assessed circulating numbers of total T lymphocytes (CD3+), helper T lymphocytes (CD3+CD4+), cytotoxic/suppressor T lymphocytes (CD3+CD8+), and B cells (CD19+). PCS1 also included assessment of circulating numbers of natural killer cells (CD32+CD16+CD56+). Lymphocyte data from both studies are expressed as absolute numbers of cells and as percentages of total white blood cells. T helper and T suppressor cells also are expressed as percentages of total T lymphocytes.
Participants provided blood samples for separation and isolation of lymphocyte subsets upon entry into quarantine, 48 hours prior to viral challenge. Samples were drawn using standard venipuncture into heparinized vacuum tubes. T cell CD marker data are available in a subsample of BCS participants (n=151 to n=182 depending on cell type).
Information is not available on the specific assay used in BCS to assess lymphocyte subsets (see Frequently Asked Questions).
Blood samples for separation and isolation of lymphocyte subsets were collected on two occasions, 1 and 2 weeks prior to quarantine. Samples were drawn using standard venipuncture into heparinized vacuum tubes and stored at room temperature until assay.
A complete blood count with differential and flow cytometry with three-color immunofluorescence1 were used to assess total white blood cells, as well as circulating numbers of total T lymphocytes (CD3+), helper T lymphocytes (CD3+CD4+), cytotoxic/suppressor T lymphocytes (CD3+CD8+), B cells (CD19+), and natural killer cells (CD32+CD16+CD56+). The Common Cold Project data set contains cell counts for each of the two blood draws (i.e., 2 weeks and 1 week pre-quarantine, respectively), as well as the average count across the two draws. Correlations between the two assessments were high (average r = .78; range .62–.82, P < .001).
Cell separation assays were performed at the Immunologic Monitoring and Diagnostic Laboratory of the University of Pittsburgh School of Medicine.
1 Kirkwood, J. M., Bryant, J., Schiller, J. H., Oken, M. M., Borden, E. C., & Whiteside, T. L. (1997). Immunomodulatory function of gamma interferon in patients with malignant melanoma: Results of a phase II-B trial in patients with malignant melanoma, ECOG Study E 4907. Eastern Cooperative Oncology Group. Journal of Immunotherapy, 20, 146–157.