- When the body is invaded by bacteria, a virus or parasites, an immune alarm goes off, setting off a chain reaction of cellular activity in the immune system.
- Macrophages or other innate immune cells, such as basophils, neutrophils, may be deployed to help attack the invading pathogen.
- Those cells often do the job, and the invader is destroyed.
Special Ops team
- Sometimes, when the body needs a more sophisticated attack, it turns to its T-cells and B-cells.
- These cells are the special ops of the immune system—a line of defense that uses past behaviours and interactions to learn to recognize specific foreign threats and attack them when they reappear.
- T cells and B cells are the two types of lymphocytes that are involved in triggering the immune response in the body.
- Both T cells and B cells are produced in the bone marrow.
- Both T cells and B cells are involved in recognizing pathogens and other harmful, foreign materials inside the body such as bacteria, viruses, parasites, and dead cells.
Types of T Cells
- The two types of T cells are
- Helper T cells
- Cytotoxic T cells
Helper T cells
- The major function of the helper T cells is to activate cytotoxic T cells and B cells.
- The severity of disease can depend on the strength of these T cell responses.
Cytotoxic T cells – destroy pathogens by phagocytosis
- B cells produce and secrete antibodies, activating the immune system to destroy the pathogens.
- The main difference between T cells and B cells is that T cells can only recognize viral antigens outside the infected cells whereas B cells can recognize the surface antigens of bacteria and viruses.
T cells and SARS COV 2
- Immune warriors (T cells) help us fight some viruses, but their importance for battling SARS-CoV-2, the virus that causes COVID-19, has been unclear.
- Now, two studies reveal infected people harbour T cells that target the virus—and may help them recover.
- Both studies also found some people never infected with SARS-CoV-2 have these cellular defenses, most likely because they were previously infected with other coronaviruses.
- Using bioinformatics tools, a team of immunologists at the La Jolla Institute for Immunology, predicted which viral protein pieces would provoke the most powerful T cell responses.
- They then exposed immune cells from 10 patients who had recovered from mild cases of COVID-19 to these viral snippets.
- All of the patients carried helper T cells that recognized the SARS-CoV-2 spike protein, which enables the virus to infiltrate our cells.
- They also harboured helper T cells that react to other SARS-CoV-2 proteins.
- And the team detected virus-specific killer T cells in 70% of the subjects
Never Infected with SARS COV 2
- In the blood from 68 uninfected people – 34% hosted helper T cells that recognized SARS-CoV-2.
- The La Jolla team detected this cross reactivity in about half of stored blood samples collected between 2015 and 2018, well before the current pandemic began.
How are these studies helpful ?
- Although the studies don’t clarify whether people who clear a SARS-CoV-2 infection can ward off the virus in the future, both identified strong T cell responses to it, which bodes well for the development of long-term protective immunity.
- The findings could also help researchers create better vaccines.
- The more than 100 COVID-19 vaccines in development mainly focus on another immune response: antibodies.
- These proteins are made by B cells and ideally latch onto SARS-CoV-2 and prevent it from entering cells.
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