24.9
Vaccinations
Overview
Vaccination is the administration of antigenic material from pathogens to confer immunity against a specific microorganism. Vaccination prime…
Vaccination, the administration of a vaccine, the antigenic material from pathogens prepares the body for future infections via specific pathogen.
When a vaccine is first administered, an antigen presenting immune cell or APC, such as a dendritic cell, engulfs the antigen from the vaccines, degrades it and displays pieces of the antigen on its surface.
APCs then activate T-helper cells or Th for short that triggers cytotoxic T lymphocytes or CTLs, also know as killer T-cells and B-cells.
Once activated, CTLs are able to detect infected cells, bind to the cells and release chemicals that kill the cells along with harbored pathogens.
Post-activation by Th, B-cells divide into plasma and memory B-cells. The plasma cells make antibodies that bind to vaccine-introduced antigens to destroy and eliminate them from the body.
After the vaccine-induced mock infection is cleared, some T-cells get converted into memory cells that can readily divide and grow whenever re-exposure occurs to the same pathogen or its antigens in the future.
The memory cells and antibodies generated via vaccines against a specific pathogen remain in the body for months or years at a time depending on the vaccine.
When an individual gets infected by the same pathogen or antigen that they were vaccinated against, the memory cells will recognize the antigen and can divide rapidly to produce a quicker immune response.
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Q1: How do antigen-presenting cells activate the immune system after vaccination?
Antigen-presenting cells (APCs) such as dendritic cells engulf vaccine antigens, degrade them, and display antigen pieces on their surface bound to MHC molecules. APCs then migrate to lymph nodes where they stimulate naive helper T cells and cytotoxic T cells. This activation triggers cell-mediated immune responses that prepare the body to recognize and eliminate the pathogen if encountered later.
Q2: What is the difference between plasma cells and memory B cells after vaccination?
After activation by helper T cells, B cells differentiate into two types. Plasma cells immediately produce antibodies specific to vaccine antigens that bind to and destroy pathogens. Memory B cells persist in the body for months or years, enabling rapid antibody production upon future exposure to the same pathogen, providing long-term immunity.
Q3: How do memory cells provide faster immune protection during reinfection?
Memory T cells and B cells generated during vaccination recognize antigens from previously encountered pathogens. Upon reexposure, these memory cells divide rapidly and mount a quicker, more efficient immune response than the initial vaccination. This accelerated response prevents or reduces disease severity when the actual pathogen is encountered.
Q4: What role do cytotoxic T lymphocytes play in vaccine-induced immunity?
Cytotoxic T lymphocytes (CTLs), also called killer T cells, are activated by helper T cells after vaccination. CTLs detect infected cells, bind to them, and release chemicals that kill the cells along with harbored pathogens. This cell-mediated response is crucial for eliminating virus-infected cells and preventing pathogen spread.
Q5: How does herd immunity protect unvaccinated individuals in a community?
Herd immunity occurs when a high percentage of the population is vaccinated against a pathogen, preventing its transmission throughout the community. Even unvaccinated individuals, including those too young or immunocompromised to receive vaccines, have reduced infection risk because the pathogen cannot find sufficient susceptible hosts to propagate.
Q6: Why does the influenza vaccine need to be reformulated annually?
The influenza virus evolves at an exceptionally rapid rate, with new viral strains emerging frequently. Because existing vaccines target specific viral strains, a new vaccine must be developed each year to match the currently circulating influenza variants and provide effective protection against infection.
Q7: What types of antigens are used in different vaccine formulations?
Vaccines contain antigens derived from specific pathogens in different forms. Inactive vaccines contain intact but non-replicating antigens, while subunit vaccines contain only pathogen fragments. Attenuated vaccines use live weakened pathogens that stimulate immune responses without causing severe disease, and many vaccines include adjuvants to enhance immune responses.