University Essay: Human Immunology and Types of Vaccination

This essay delves into the realm of human immunology, specifically focusing on the various types of vaccinations. It begins with an introduction to the immune system, differentiating between the innate and adaptive systems, and explaining how immunizations stimulate immunity by introducing antigens that trigger immune responses. The essay then elaborates on the three major types of vaccines: live attenuated vaccines (LAVs), killed or inactivated vaccines, and subunit vaccines. LAVs, derived from weakened pathogens, offer robust immune training, while killed vaccines, produced from inactivated microbes, provide a safer alternative. Subunit vaccines, containing only antigenic components, minimize adverse reactions. The essay concludes by emphasizing the importance of further research to enhance awareness of vaccines' protective role in strengthening the immune system against infections.

Running head: Human Immunology 1
Human Immunology
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Human Immunology 2
Types of vaccination
Introduction
Vaccination is the inoculation of antigen or vaccine into the body whereas immunization is the
actual process of inducing an immune response which can be cell-mediated or humoral in the
recipient. The elements of the immune system can be broken down into two major categories
namely, the innate resistance system which includes the skin, mucosal barriers and phagocytes,
and the adaptive system which is comprised of humoral and cellular immunity. Both of these
systems exist in constant interaction to ensure that there is an effective immune response.
Immunizations stimulate body immunity through specific mechanisms after the body has first
spotted the threat to be either immunization or a pathogenic agent. The innate immune system
plays an important role in the early detection; however, B-cells undertake this function. The
process of detection starts once the immune system detects epitopes on antigens after which
multiple processes of the innate immune system will provide an appropriate feedback to the
issue. Then the mechanisms of the innate immunity become attached to the agent and help in its
elimination by antigen-presenting cells which develops the antigens from the current microbe
and add in the resultant antigen alongside the MHC protein onto the cell’s surface of the resultant
antigen.
In the case of a viral antigen, it will be engulfed with MHC I protein and processed by the
resulting cell to a CD8 cell which will possibly activate cell-mediated immunity. For parasitic
antigen or bacterial, the MHC II protein will engulf the antigen and processed by the antigen-
presenting cell to a CD4 cell which will probably activate antibody-mediated immunity. There
are three major types of vaccines namely Live Attenuated Vaccines (LAVs), killed or inactivated
vaccine, and a subunit vaccine. The LAVs are derived from already weakened disease-causing

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pathogens such as vaccines against mumps, chickenpox and measles. Killed vaccines are
produced from already killed disease-causing microbe using physical or chemical processes.
They are more stable than LAVs. Example include vaccines against hepatitis A, influenza among
others. Subunit vaccines are like the killed vaccines but the only difference is that they only
contain the antigenic components of the pathogen. An example is the Hepatitis B vaccine (Clem,
2011).
With the current increase in the rate of infection and multiple forms of diseases, there is a need to
explore further on human immunology with a particular emphasis on vaccination. This essay will
examine in details the major types of vaccination.
Mechanisms by which Immunization stimulate Immunity
Antigens are elements of proteins found in disease-causing micro-organisms and the vaccines
made to fight them. The antigens trigger multiple cells in the immune system in addition to
macrophages, B and T cells. The ingestion of antigens by macrophages marks the beginning of
an immune response. The Major Histocompatibility Complex (MHC) transports some of the
antigen fragments, after being broken down by macrophages, to the cell’s surface, where they are
exposed but still bound to the MHC molecule. The exposed antigen fragments are identified by T
cells, which trigger B cells to release antibodies to the fragments and further stimulate other
immune mechanisms. In the case of a viral antigen, it will be bound with MHC I protein and
processed by the resulting antigen cell to a CD8 cell which will possibly activate cell-mediated
immunity. For parasitic antigen or bacterial, the MHC II protein will engulf the antigen and
processed by the final antigen cell to a CD4 cell which will probably trigger antibody-mediated
immunity (Pulendran & Ahmed, 2011).

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Activated immune cells produce several different chemical compounds referred to as cytokines,
which determine the nature of antibodies to be secreted. For instance, cytokine interleukin 4
trigger B cells to produce immunoglobin E antibodies responsible for prompting allergic
feedbacks. Diverse MHC compounds are attached to other antigen fragments hence the reason
why the immune system of two individuals may respond differently to a particular protein in a
vaccine due to the varying components of a similar protein. This explains the variations in
reactions to antigens (Clem, 2011).
Types of Vaccines
The common categories of vaccines include Live Attenuated Vaccines (LAVs), killed or
inactivated vaccine, and a subunit vaccine. The LAVs are derived from already weakened
disease-causing pathogens such as vaccines against mumps, chickenpox and measles. In other
words, the LAVs comprise a type of the living microorganism that has chemically been
deteriorated to prevent it from causing disease. These vaccines are the best “trainers” of the
immune system because they closely resemble an ordinary infection. Moreover, they generate
effective cellular and antibody reactions and are effective in generating long-term immunity with
a single dose. It is relatively easy to produce LAVs with viruses than bacteria since the former
have limited genes thus making the management of viral features easy. However, it requires
refrigeration to maintain effectiveness and thus increasing the chances of reversion to the initial
state of infection. The examples of LAVs include those against chickenpox, measles and mumps.
Killed vaccines are produced by scientists by killing the microbe that causes the disease using
radiation, chemicals or heat. Killed vaccines are much safer and more stable due to inactivation
than LAVs because dead microbes can't mutate back to their infectious active state. They do not
require refrigeration and can thus be transported easily. On the other hand, the inactivated

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vaccines generate weaker immune responses thus necessitating the need for other boosters to
maintain immunity. Examples of killed vaccines include those against hepatitis A, influenza,
rabies and polio. Subunit vaccines are just like killed vaccines with the exception that they only
contain antigenic components of the pathogen. In other words, Subunit vaccines consist of only
the antigens that best optimize the immune system. They minimize the possibility of adverse
reactions because they only make use of a few specific antigens. On the contrary, such
specificity makes it difficult to ascertain the antigen which should be incorporated into the
vaccine. An example is the plague immunization (Clem, 2011).
Conclusion
The immune system is made up of components that exist in constant interaction to ensure that
there is an effective immune response. The innate resistance system is responsible for the initial
detection; however, B-cells undertake this function. The adaptive system, on the other hand, is
responsible for humoral and cellular immunity. The antigens trigger multiple cells in the immune
system in addition to macrophages, B and T cells. The ingestion of antigens by macrophages
marks the beginning of an immune response after which the MHC transports some of the antigen
fragments to the surface of the cell where they are detected by the T cells which trigger B cells to
release antibodies to the fragments and further stimulate other immune mechanisms. The
commonly used vaccines include Live Attenuated Vaccines (LAVs), killed or inactivated
vaccine, and subunit vaccine with LAVs being more effective than the rest. There is a need for
further research to foster awareness on the role of the vaccine as a protective mechanism. This
would help in strengthening the immune system thus protecting it from existing multiple
infections.

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References
Clem A. S. (2011). Fundamentals of vaccine immunology. Journal of global infectious
diseases, 3(1), 73–78. doi:10.4103/0974-777X.77299.
Pulendran, B., & Ahmed, R. (2011). Immunological mechanisms of vaccination. Nature
immunology, 12(6), 509–517. doi:10.1038/ni.2039