Critical Reasoning Practice Set-1

Monday, April 19th, 2021

Immune System

A study published in Nature Medicine suggests that antibodies formed against SARS-CoV-2 begin to decrease in number, just two-three months after infection. “We observed that IgG levels and neutralizing antibodies in a high proportion of individuals who recovered from SARS-CoV-2 infection start to decrease within two-three months after infection,” Quan-Xin Long from Chongqing Medical University, Chongqing, China and others write.

(2)In contrast, circulating antibodies against 2002-2003 SARS and MERS coronavirus were found to last more than one year. In the case of the 2002 SARS, sustained IgG levels were seen for more than two years after infection, while antibody response lasted for nearly three years in the case of MERS.

(3)This does not necessarily mean that people previously infected with SARS-CoV-2 can be reinfected soon after. Even if the antibody level decreases, it might be protective. “A person with low antibody level can get reinfected but the viral load will be low, infectivity will be less and he/she may not progress to a diseased state,” says virologist Jacob John formerly with CMC Vellore. “Antibodies specific to a virus even when present in low levels will be protective against disease.”

(4) Besides inducing neutralising antibodies, novel coronavirus has also been found to induce cellular immunity. As a result, the immune system’s T cells and B cells are elevated in an infected person. “Generally, when antibody levels are high, the T cells are low and vice versa,” says Dr. John.

(5)When infected by a virus, non-specific immune response in the form of macrophages, neutrophils and other cells tend to prevent the virus from causing symptoms. Soon after, the body makes antibodies specific to the virus called the immunoglobulins — IgG and IgM, called the adaptive response. In addition, the cellular immunity kicks in when the body makes T cells that destroy cells that have been infected by the virus. The combination of adaptive response and cellular immunity “may prevent progression to severe illness or re-infection by the same virus. This process is often measured by the presence of antibodies in blood,” WHO says.

Source with edits and revisions:

Questions

1. Which of the following can be inferred from the passage?
a. A person having antibodies against MERS is totally safe from re-infection
b. Only humans can develop antibodies against viruses
c. There are only two kinds of immune system in a human body.
d. Our cellular immune system is designed to destroy the bad cells if needed.

 

2. Which of the following can’t be inferred from the passage?

a. One virus is not as deadly as a million viruses.
b. A person can get re-infected from Covid-19 virus
c. A person can’t get re-infected from MERS virus.
d. Antibodies developed in response to a virus in a human body decreases with time.

3. What is the conclusion of the third paragraph of the passage?

a. A person with low antibody level can get re-infected but the viral load will be low
b. People previously infected with SARS-CoV-2 can be re-infected soon after
c. Antibodies specific to a virus even when present in low levels will be protective against disease.
d. When the infectivity will be less and a person infected with virus may not progress to a diseased state.

 

4. What is the role played by the claim that the combination of adaptive response and cellular immunity “may prevent progression to severe illness or re-infection by the same virus, in the argument?

a. It acts a a premise for the argument.
b. It acts as a conclusion for the argument
c. Neither A nor B
d. Both A and B

 

5. ‘Government of UK issuing certificates to people infected with virus who have developed antibodies’, which of the following statements, if true, would justify the policy enacted by the government?

a. People who have survived the virus are ignorant about the safety measures as they feel they are immune to the virus now.
b. Many countries have successfully contained the viral load to a negligible level
c. South Korea is seeing resurgence of infections, especially amongst those infected earlier.
d. The average age of people dying in UK due to covid-19 is lower than the age of average people dying from covid-19 across the world.

 

Answers

1. D
2. C
3. C
4. B
5. C