Immunity Against Covid-19
Why in News
As per a recent study, published in the journal Science, based on analyses of blood samples from 188 patients, Covid-19 survivors have protective immunity from the coronavirus for months, perhaps years, after infection.
Key Points
- Background:
- The duration of immunity to Covid-19 has been a subject of research throughout the pandemic, and studies so far have provided various results.
- Previously in July 2020, a study suggested that immunity might be lost in months making it susceptible to re-infections.
- Findings of the New Study:
- It suggests that the body’s immune response to the novel coronavirus can last for at least eight months after the onset of symptoms from the initial infection.
- It suggests that nearly all Covid-19 survivors have the immune cells necessary to fight re-infection.
- It measured antibodies, memory B cells, helper T cells and killer T cells all at the same time.
- It addresses concerns arising out of Covid-19 data from other labs, which showed a dramatic drop-off of Covid-specific antibodies over time.
Immunity
- Meaning:
- Immunity is the ability of the body to defend itself against disease-causing organisms.
- Immunity is of two types: Innate immunity and Acquired immunity.
- Innate Immunity:
- It is a non-specific type of defense that is present at the time of birth.
- Acquired Immunity:
- It is pathogen specific. It is characterized by memory. This means that the body when it encounters a pathogen for the first time produces a response called primary response which is of low intensity.
- Subsequent encounters with the same pathogen elicits a highly intensified secondary or anamnestic response. This is ascribed to the fact that the body appears to have memory of the first encounter.
- Antibody:
- An antibody, also known as an immunoglobulin, is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses.
- T cells (thymus cells) and B cells (bone marrow- or bursa-derived cells) are the major cellular components of the adaptive immune response. T cells are involved in cell-mediated immunity, whereas B cells are primarily responsible for humoral immunity (relating to antibodies).
- Memory B cells (MBCs):
- These are a B cell subtype formed within germinal centers following primary infection. MBCs can survive for decades and repeatedly generate an accelerated and robust antibody-mediated immune response in the case of re-infection (also known as a secondary immune response).
- Helper T cells:
- These are arguably the most important cells in adaptive immunity, as they are required for almost all adaptive immune responses. They not only help activate B cells to secrete antibodies and macrophages to destroy ingested microbes, but they also help activate killer T cells to kill infected target cells.
- Killer T cells:
- It is a T lymphocyte (a type of white blood cell) that kills cancer cells, cells that are infected (particularly with viruses), or cells that are damaged in other ways.