Phenotypic features of adaptive immune system cells in
COVID-19
A representative figure for flow cytometric evaluation of lymphocyte
subsets was shown in Figure 4. All percentages and the absolute numbers
of lymphocyte subsets was given in Table 2.
The percentage and the absolute number of B lymphocytes
were extremely low in all groups of COVID-19 patients: The percentage
of B lymphocytes evaluated by surface CD19 was low in all COVID-19
patients compared to control (p <0.01, Figure 4b, Table 2).
There was no difference among patient groups. Furthermore, when the
absolute B lymphocyte counts were examined, the number of B lymphocytes
was found to be remarkably decreased in patients with COVID-19
(p<0.02, Table 2). In the severe group, the number of B
lymphocytes decreased up to approximately one-fifth of the control. CD19
and CD138 were stained in a few patients with the thought that the
reason for this extreme reduction may be the result of the
differentiation of B lymphocytes into plasma cells. However, no CD138
positive plasmablast was found in the periphery.
The absolute number of T cells gradually decreased
according to the severity of the disease: A significant increase in
the percentages of T cells
(CD3+CD16-CD56-)
was found in the mild group of patients with Covid-19 in comparison to
the severe group and healthy control, as well (p<0.01, Table
2, Figure 4c). The absolute number of T cells was in the normal range in
only the mild group of patients whereas this was found to be decreased
in both moderate and severe groups in comparison to the mild group of
patients and controls (p<0.01, Table 2).
No difference in the percentage of T helper cells but its
number decreased in the moderate and severe COVID-19 groups: The
percentage of CD3+CD4+ T cells was
not different among the groups (Table 2, Figure 4d). The absolute number
of CD3+CD4+ T cells was in the
normal range in the mild group. But, this was significantly reduced in
moderate and severe disease courses in comparison to controls and also
mild disease course (p<0.01; p<0.02 respectively,
Table 2).
A normal number of T cytotoxic/suppressor cells with an
increased percentage in the mild group decreased with the disease
severity: The percentage of
CD3+CD8+ cytotoxic/suppressor T
cells was found to be elevated in the mild group in comparison to severe
patients (p<0.03) and controls, as well (p<0.01;
Table 2, Figure 4e). Thus, it was shown that the reason for the increase
in the percentage of CD3+T cells in the mild group was
due to the increase of CD8 + T cells. The absolute
number of CD3+CD8+ T cells was in
the normal range in the mild group. But, this was significantly
decreased in the moderate and severe groups in comparison to the mild
group and healthy controls (p<0.01, Table 2).
When the CD4 +CD8+ double-positive
cells and the ratio of CD4/CD8 were examined among all the groups, no
difference was detected.