Immune cell phenotyping in low blood volumes for assessment of cardiovascular disease risk, development, and progression: a pilot study

Abstract

Background: Cardiovascular disease (CVD) is the leading cause of death in the world. Given the role of immune cells in atherosclerosis development and progression, effective methods for characterizing immune cell populations are needed, particularly among populations disproportionately at risk for CVD. Results: By using a variety of antibodies combined in one staining protocol, we were able to identify granulocyte, lymphocyte, and monocyte sub-populations by CD-antigen expression from 500 µl of whole blood, enabling a more extensive comparison than what is possible with a complete blood count and differential (CBC). The flow cytometry panel was established and tested in a total of 29 healthy men and women. As a proof of principle, these 29 samples were split by their race/ethnicity: African-Americans (AA) (N = 14) and Caucasians (N = 15). We found in accordance with the literature that AA had fewer granulocytes and more lymphocytes when compared to Caucasians, though the proportion of total monocytes was similar in both groups. Several new differences between AA and Caucasians were noted that had not been previously described. For example, AA had a greater proportion of platelet adhesion on nonclassical monocytes when compared to Caucasians, a cell-to-cell interaction described as crucially important in CVD. We also examined our flow panel in a clinical population of AA women with known CVD risk factors (N = 20). Several of the flow cytometry parameters that cannot be measured with the CBC displayed correlations with clinical CVD risk markers. For instance, Framingham Risk Score (FRS) calculated for each participant correlated with immune cell platelet aggregates (PA) (e.g. T cell PA β = 0.59, p = 0.03 or non-classical monocyte PA β = 0.54, p = 0.02) after adjustment for body mass index (BMI). Conclusion: A flow cytometry panel identified differences in granulocytes, monocytes, and lymphocytes between AA and Caucasians which may contribute to increased CVD risk in AA. Moreover, this flow panel identifies immune

Health Disparities in COVID-19: Addressing the Role of Social Determinants of Health in Immune System Dysfunction to Turn the Tide

“…While increasing NK cell numbers might sound like an enhancement of immune cell function, the opposite is true when additional NK cell subset changes or functional changes are present. We found decreased levels of “cytotoxic” NK cells (CD56 hi /CD16 dim ) and increased levels of “proliferative” NK cells (CD56 dim /CD16 hi ) within the overall NK cell populations among non-Hispanic Black as compared to Caucasian blood donors ( 47 ). This shift in NK cell subsets is indicative of a loss of NK cell “killing” ability and could potentially be linked to a delayed or decreased response to an acute viral infection, like SARS-CoV-2.…”

“…Amongst all immune cells, T cells, monocytes, and NK cells are taking a center stage in COVID-19 severity ( 41 – 44 ), recovery ( 45 ), and mortality ( 46 ), indicating that disturbed baseline T cell, monocyte or NK cell function might hinder adequate response to SARS-CoV-2 infection. In the past, our group and others have demonstrated racial/ethnic differences in immune cell distribution and cytokine levels ( 47 – 52 ). For instance, we and others showed shifts in monocyte subsets in non-Hispanic Blacks toward intermediate (CD14 − /CD16 + ) and non-classical (CD14 + /CD16 + ) monocytes accompanied by a decrease in classical monocytes (CD14 + /CD16 − ) as compared to Caucasians.…”

“…We hypothesize that this subset shift could relate to more severe COVID-19 outcomes in non-Hispanic Blacks, especially as the pro-inflammatory, non-classical (CD14 + /CD16 + ) monocyte subset can play an important role in the inflammatory storm observed in severe COVID-19 ( 42 ) and has been postulated as potentially crucial in separating mild from severe COVID-19 cases ( 53 ). Additionally, we have recently demonstrated in a small hypothesis-generating study that the NK cell profile of non-Hispanic Black blood donors differs significantly from that of Caucasian blood donors ( 47 ). Overall NK cell proportions were increased in non-Hispanic Black blood donors.…”

Multilevel mobile health approach to improve cardiovascular health in resource-limited communities with Step It Up: a randomised controlled trial protocol targeting physical activity

“…We will also collect blood samples to evaluate effects of PA changes on immune cells involved in CVD and the chronic stress response. Specifically, we will perform flow cytometry panels to (1) characterise the overall immune cell profile, 70 (2) analyse monocyte subsets and receptor expression (known to be critically involved with atherogenesis) [71][72][73] and (3) identify natural killer cell subsets (known to be deactivated with social stress and obesity). 74 We will profile immunoregulating proteins from participants' serum alongside stress-induced neurotransmitters and other proteins associated with CVD progression (table 1).…”

COVID-19: Growing Health Disparity Gaps and an Opportunity for Health Behavior Discovery?

“…Furthermore, immune responses to adverse psychosocial and environmental conditions may contribute to an increased risk of COVID-19 morbidity and mortality among African Americans. 18,19 Specifically in relation to COVID-19, interleukin-6 (IL-6), an inflammatory cytokine associated with chronic stress and with demonstrated racial/ethnic differences, appears to be a key mechanism involved in COVID-19 disease severity. In particular, an association between the sympathetic nervous system hormone adrenaline and IL-6 is found in conditions with increased COVID-19 mortality and underlying chronic diseases disproportionately found among African Americans, including cardiovascular disease, 20 diabetes, 21 and hypertension.…”