Naturally activated adaptive immunity in COVID-19 patients
Related Experiment Video
Updated: Dec 7, 2025
Contact-Free Co-Culture Model for the Study of Innate Immune Cell Activation During Respiratory Virus Infection
Published on: February 28, 2021
Xiaofeng Yang1, Tongxin Dai2, Xiaobo Zhou1,3
1Department of Pathogenic Microbiology and Immunology, School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, Xi'an, Shaanxi, China.
Insights
COVID-19 patients show altered adaptive immunity, with increased T and B cell activation and specific cell population changes. These findings suggest a functional immune response in most individuals during SARS-CoV-2 infection.
Area of Science:
- Immunology
- Virology
- Hematology
Background:
- The global spread of COVID-19 necessitates understanding its immunological impact.
- Limited data exists on adaptive immune cell changes in COVID-19 patients.
Purpose of the Study:
- To analyze adaptive immune cell populations and phenotypes in COVID-19 patients.
- To investigate the functional status of T and B cells during SARS-CoV-2 infection.
Main Methods:
- Blood samples were collected from 38 COVID-19 patients and 18 healthy donors.
- Flow cytometry was used to analyze lymphocyte populations and cell surface markers (CD25, PD-1).
Main Results:
- COVID-19 patients exhibited decreased lymphocyte percentages, increased B cell percentages, and similar CD4/CD8 T cell ratios compared to healthy donors.
- Activated and exhausted T cells (CD8+ T cells expressing CD25 and PD-1) were observed.
- Increased percentages of T follicular helper and germinal center B-like cells were noted in patients.
- Immune parameter changes were consistent across different age groups.
Conclusions:
- SARS-CoV-2 infection activates T and B cells, indicating functional adaptive immunity.
- The immune system appears primed to respond to SARS-CoV-2 infection in most patients receiving medical care.
Abstract:
Coronavirus disease-2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus (SARS-CoV-2) has rapidly spread worldwide, threatening the health and lives of many people. Unfortunately, information regarding the immunological characteristics of COVID-19 patients remains limited. Herein, we collected blood samples from 18 healthy donors (HDs) and 38 COVID-19 patients to analyse changes in the adaptive immune cell populations and their phenotypes. We observed that the lymphocyte percentage moderately decreased, CD4 and CD8 T cell percentage among lymphocytes were similar, and B cell percentage was increased in COVID-19 patients in comparison to that in HDs. T cells, especially CD8 T cells, showed an enhanced expression of late activation marker CD25 and exhaustion marker PD-1. Importantly, SARS-CoV-2 infection increased the percentage of T follicular helper- and germinal centre B-like cells in the blood. The parameters in COVID-19 patients remained unchanged across various age groups. Therefore, we demonstrated that the T and B cells are activated naturally and are functional during SARS-CoV-2 infection. These data provide evidence that the adaptive immunity in most patients could be primed to induce a significant immune response against SARS-CoV-2 infection upon receiving standard medical care.
Related Concept Videos
01:29Immune Response Against Viral Pathogens
NK Cells
NK cells are a crucial part of our innate immune system, acting as the first line of defense against viral infections. These cells can recognize and kill infected cells without prior exposure to the virus, effectively slowing down the spread of infection. Additionally, NK cells produce proinflammatory...
01:21Introduction to Innate and Adaptive Immunity
Innate immunity is the body's natural, nonspecific defense system that acts quickly to protect against pathogens. It incorporates physical barriers like skin and mucous membranes and cellular elements such as phagocytes and natural killer cells. This part of our immune system provides an immediate,...
01:40Cell-mediated Immune Responses
01:24B Cell Activation and Differentiation
When naive B cells encounter a specific antigen that can bind to the B cell receptor (BCR) on their surface, they undergo sensitization to respond to the antigen's presence. Sensitization begins with...
01:22T Cell Activation and Clonal Selection
Naive T cells that have not yet encountered an antigen express two primary CD...
01:20Special Features of Adaptive Immunity
The primary cell types involved in adaptive immunity are T cells and B cells. Each type has a unique role in defending the body against pathogens. T cells are responsible for cell-mediated immunity. They identify and eliminate infected cells directly,...