A study has revealed that patients with severe COVID-19 who have detectable plasma cells in the peripheral blood have better survival despite adjusting for covariates correlated with disease severity.
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What Are Plasma Cells?
Plasma cells are a type of immune cells that make
large amounts of specific antibodies. These plasma cells develop from B cells
that have been activated. Plasma cells are white blood cells called plasmacyte.
The plasma cells are differentiated B-lymphocyte white
blood cells that are capable of secreting immunoglobulin or antibody. These
cells play a significant role in adaptive immune response – being the main
cells that are responsible for humoral immunity.
Without the plasma cells, a person is said to have
agammaglobulinemia and is highly susceptible or at high risk of recurring
infection. The hematopoietic lineage, structure and function of plasma cells
are evaluated, along with the clinical presentations arising from improper
plasma cell growth and development.
These plasma cells develop from antigen-activated B
lymphocytes in secondary lymphoid organs, like the spleen and lymph nodes, following
antigenic stimulation. Blimp-1, IRF4, and XBP-1 transcription factors are known
to be essential in the differentiation of mature B cells into plasma cells.
Experts have identified hospitalized adult patients
with confirmed SARS-CoV-2 infection and stratified by presence of plasma cells
and World Health Organization or WHO disease severity using the Johns Hopkins
COVID-19 Precision Medicine Analytics Platform Registry. To identify plasma
cells, a sensitive flow cytometric screening method for highly fluorescent
lymphocytes was applied and confirmed microscopically.
Lastly, time to death and time to clinical improvement
by the presence of plasma cells in patients with severe disease were assessed
using the Cox regression models.
These plasma cells were identified in 371 of 2,301
hospitalized patients with COVID-19. Patients with plasma cells were more likely
to have severe disease, but 86.6% developed plasma cells after the onset of
severe disease.
Following the adjustment for age, gender, body mass
index (BMI), race or ethnicity, and other covariates correlated with the
disease severity, those patients with plasma cells were found to have a lower
risk of mortality.
Moreover, no significant correlation was observed
between the presence of plasma cells and time to clinical improvement.
Researchers said that, “further investigation is
warranted to understand the role of plasma cells in the immune response to
COVID-19.”
The cytokines in severe COVID-19 are connected to
proliferation, differentiation, and survival of plasma cells. The cells are not
routinely found in peripheral blood; however, these may produce virus-neutralizing
antibodies later in the course of an infection according to experts.
Source: Am J Med 2021;134:1029-1033