Pathogens and Immunity in Nursing

This article discusses pathogens, their categories, and the diseases they cause. It also explores the role of resident flora in protecting the body against diseases. The article further explains the process of blood clotting and the importance of vitamin K. It delves into the differences between antigens and antibodies, as well as the types of immunity - humoral and cellular. Finally, it introduces the clonal selection hypothesis in the context of immune response.

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BIOLOGY ASSESSMENT
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The pathogen is an infectious biological agent that invades a host organism and produce disease
leading to illness (Birla et al., 2018). There are distinct categories of pathogens like virus,
bacteria, fungi, and protists or protozoa that cause varied diseases. For example athlete’s foot is
caused by fungus which causes ringworm and jock itch, Norovirus infection is caused by virus,
malaria by parasite in the order protists or protozoa and Methicillin-resistance staphylococcus
aureus (MRSA) disease is caused by bacteria specifically staph type which is very resistance to
most antibiotics for treating normal staph infection (Aldory, Ali, and Sultan, 2018).
Athlete’s foot disease mostly occurs to individuals whose feet produce a lot of sweet while
wearing very tight shoes. The feet turn to a scaly rash as a sign of infection which finally
becomes itchy, burning as well as stinging. Athlete foot can be spread from one person to
another via clothing, floors, and towels that have contamination of the fungus.
Malaria is a disease caused by various types of Plasmodium that is P. ovale, P.vivax, P.
falciparum, and P. malariae. The infectious Plasmodium is carried by female Anopheles
mosquito and once infected mosquito bites healthy individual it passes the parasite, hence one
fall sick. Norovirus infection is the most cause of gastroenteritis, and it is difficult to diagnose
the virus causing the disease.
The disease-causing agent penetrates the host via different routes which include oral, direct
contact, vector, aerosol and fomite. Oral entails the consumption of pathogenic microorganism
via contaminated feed, water and environmental material that are contaminated. Direct contact is
where the pathogenic agent attacks the exposed susceptible host by biting the skin, open wounds,
nose to nose and even the mucous membrane. Vector also, transmit diseases by transporting the
pathogenic agent to the vicinity of the host (Stanev, and Moustakas, 2019).

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Resident flora refers to the microorganism that occupies a specific part of the body. They
colonize a specific part and multiply extremely such that they outnumber the cells of the host of
human cells with a ratio of 10 to 1 (Su, Huang, and Pearce, 2019). Resident flora plays a key role
in protecting the body against disease-causing agent because they help to fight pathogen as well
as maintaining homeostasis. Also, studies reveal that some of the resident flora can mediate the
fermentation of glycerol that is naturally produced by the skin to hinder the growth of P. acnes.
Resident flora offers protection to the host by acting as a barrier towards the access of the skin by
other harmful diseases causing agent.
Resident flora also causes diseases in case there are injuries in a place where the resident flora
are not supposed to enter. If they enter they cause disease in that area and also if a person
receives antibiotics that interfere with the system of the body such that some resident flora is
stimulated to cause an infection. Similarly, surgery in an area like small intestine permits the
resident flora to come into contact with vulnerable areas like the abdomen and lead to harmful
infection (Levy, and Allegretti, 2019).
Skin is a natural barrier that hinders so many pathogenic agents that causes infection from
entering the body. It is good to know that skin is the largest organ in the body and covers the
enter part of the outer body. Skin having several layers. Makes it hard for the pathogen to
penetrate to the soft part of the body where they can cause infection.
The mucous membrane is also a natural blockage for the entrance of the disease-causing agents.
Examples of the body part where the mucous membrane occurs are nose, mouth, and eyelids.
Naturally, there is a coat of secretions that occur in the mucous membrane that are responsible
for fighting the pathogenic microorganism. These secretions also protect the body against dirt
entry as well as keeping the surface hydrated.

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Blood clotting is one of the processes that reduce blood loss when a blood vessel is injured. The
process is triggered by an injury to the blood vessel where the platelets (thrombocyte) assembles
into the vicinity. It encompasses the formation of the clot that seals the place where an injury
occurs. Several clotting factors are involved that helps to produce a long lasting clot that stops
further loss of blood (Srihirun, Schechter, and Piknova, 2019). Blood clotting has several stages
which include:
Formation of prothrombinase which can be formed either intrinsically or extrinsically but both
processes entails interaction between coagulation factors. Prothrombinase enzyme converts the
protein prothrombin into its an active form which is thrombin form, an enzyme. The thrombin
formed in turn leads to conversion of fibrinogen into its active form fibrin. The fibrin so formed
is insoluble and can form threads that bind the clot.
The diagram below illustrates the process starting from the injury of the blood vessel, then blood
vessels contracts to reduce the flow of blood to the damaged vessel. Platelet in the blood stick at
the damaged place and form a platelet plug. Further, several chemical reactions occur to form a
stable fibrin clot (Wilson, Neuenschwander, and Chou, 2019).
figure 1: the process of blood clot formation

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Vitamin K is essential for the manufacture of numerous proteins that are involved either in
coagulation or anticoagulation. Deficiency of vitamin k is shown by excessive bleeding when a
blood vessel is injured while the blood proteins control bleeding. The air is important because it
increases the rate of drying of the clot and the platelet plug as well.
A non-specific macrophage is an immune cell that can respond to several types of antigen are
usually at the forefront when it comes to body defense. They give a response to any foreign
invader using a similar mechanism. Non-specific macrophage occurs randomly to the body and
is always ready to act against foreign invasion by engulfing them and destroying completely.
Non-specific macrophage also is responsible for alerting the body immune system to any
pathogenic invasion (Eberhardt, Sanmarco, and Aoki, 2019). When an antigen invades the body,
non-specific macrophage presents protein on the cell surface known as an antigen. The antigen,
in turn, signals the presence of the antigen to the t helper cells that stimulate the B cells of the
immune system to produce antibodies.
The antigen is any molecule that causes the body immune system to produce antibodies against
it. Each antigen bears different surface features, or epitopes, that makes antigen to be specific in
response (Ternant et al., 2019). Antigen can either originate from inside the body or external
environment. While antibody is a glycoprotein that is normally secreted in response to invading
foreign particles called antigen like microbes and viruses (Chen et al. 2019). The antibody is thus
an essential part of the immune system’s defense against any infection as well as disease.

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Figure 2: The structure of antibody and antigen binding
Immunity is the ability of a multicellular organism to reject infective microbes from penetrating
it. Immunity comprises of both specific and non-specific elements. Non-specific elements act as
a hindrance or eradicators of a large number of pathogenic microbes regardless of their antigenic
composition (Iwanaga, and Kolls, 2019).
Innate immunity or native immunity occurs by an organism make-up, that is its genetic
composition, without extrinsic stimulation or previous infection. Innate immunity is divided into
two that is specific innate immunity that involves resistance to a certain type of microbe only.
Non-specific one is a degree of opposition to all infections regardless of the kind (Loering,
Cameron, Starkey, and Hansbro, 2019).
Adaptive immunity is categorized according to the method of introduction of immunity like
naturally acquired via chance contact with a pathogenic agent or can be artificially acquired
immunity which develops via deliberate actions like vaccination. Naturally and artificially

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acquired immunity can be further categorized depending on whether the host organism
developed immunity itself by antigen referred to as active immunity which can last for a long
time or even lifelong.
Passive immunity, on the other hand, is acquired via transfer or injection of activated T-cells or
antibodies originating from an immune host; it lasts only for a short period like months. Adaptive
immunity is also categorical on the bases of immune mediators involved that is either humoral
immunity or cellular immunity. Humoral immunity is the immunity that is mediated by the
extracellular body secretions like antibodies while cellular immunity is a defense that is
stimulated by the body cells themselves, for example, the T-cells.
The diagram below illustrates the division and summary of the discussed type of immunity
(Rostøl, and Marraffini, 2019):

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Differences between antigen and antibody (Chow et al., 2019).
Antigen Antibody
Origin Occurs within the body or
externally
Occurs within the body
Overview A substance that can induce an
immune response
Proteins that recognize and
bind to antigens
Specific binding site Epitope Paratope
Molecule type Usually, proteins may also be
polysaccharides, lipids or
nucleic acids
Proteins
Image or structure
The structure of the antibody molecule
The antibody is a Y-shaped molecule comprising of three equal-sized portions, lightly linked by
a flexible rope. Every antibody comprises of four polypeptides that is two light chains and two
heavy chains, linked to form a Y-shaped molecule (Varkey et al., 2019).

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It is secreted from the B-cell receptor and is thus identical to B-cell receptor of the cell that
produces it apart for a minor portion of the C-terminus of the heavy chain. The two arms of the Y
end area they vary and are not of the same size and can only bind to a specific antigen. The main
divisions of an antibody are the heavy chain, light chain, variable constant and antigen binding
site. The variable constant area is composed of both light and heavy chains (Peng et al., 2019).
Humoral and cellular mediated immunity
Humoral immunity also is known as antibody-mediated immunity because the antibodies are
involved in providing immunity in this case. The humoral immunity deals with the pathogens
that are mobile outside the cells that are already infected. The immunity occurs when the
antibodies produced by the B-cells bind with the antigens that invade the healthy body to cause
disease, and the antibody destroys them. The destruction of the antigen is by causing them to lyse
or burst as well as phagocytosis (Ganeshpurkar, and Saluja, 2018).
Cellular immunity is brought about by the cells, and it takes place inside the cell, hence the name
cellular immunity. T-lymphocytes cells are responsible for this kind of immunity where they
help the B-cells to differentiate and produce antibodies against the invading antigen. The helper
T-cell produces cytokines that assist in the activation of T cells bind to the invaded cells to form
an antigen complex. The T cells later differentiate into cytotoxic T cells causing the infected
cells to lyse or burst, thus preventing the body from falling sick (John et al., 2018).
Differences between humoral and cell-mediated immunity (Tiner et al., 2016).
Humoral/antibody mediated immunity Cellular mediated immunity

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Antibodies are produces during humoral
immune response
No antibodies formed in cellular immune
response
B-cells secrete antibodies which bind with the
antigen and neutralize them.
Here the T-cell receptors bind to the T-cell and
afterward the T-cell themselves bind to the
antigen.
Offers protection against extracellular bacterial
and viral pathogens.
Offers protection against virus, fungi and
intracellular bacterial foreign invaders.
Antibodies are responsible for the detection of
antigen in humoral immunity.
T-cell receptors are involved in the detection of
any foreign invader.
Only TH cells are involved in producing a
response.
Several cells to produce immune response are
involved that is CD8 + CD4 and T-cells.
It is not able to eradicate the tumor cells. It can eradicate the tumor cell, therefore, can
offer immunity against cancer.
Humoral immunity cannot offer
immunological surveillance.
Cellular immunity is able to provide
immunological surveillance.
Similarities between humoral and cellular immunity:
1. Both humoral and cellular-mediated immune system are vigorous immunities
2. In both cases of immunity, there is a stage called lag period

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3. Both humoral and cellular immunity are efficient and efficient towards numerous kinds
of microorganisms that cause diseases.
4. In both cases, there is the presence of immunological memory
5. For the cases of immune deficient person, both immune systems are ineffective.
Clonal selection hypothesis
Clonal selection theory is used to explain how the cells involved in the immune response can
secrete enough quantity of the needed antibodies. It concentrates its topically on the functions of
lymphocytes cells in response to particular antigens that invade the body. The idea of clonal
selection was invented by an Australian doctor called Frank Macfarlane Burnet in 1957 (O’Leary
et al., 2018). He was attempting to explain the process of production of different types of
antibodies.
Studies show that the theory has been broadly accepted model of explaining how the immune
system reacts to foreign invaders and how the T and B lymphocytes are produced for the
destruction of specific antigens. It states that in the pre-existing group of immune cell
particularly the B- cell, where specific antigen selects its counter-specific cell to cause
multiplication to produce clones or the antibody secretion (Würth et al., 2018).
The stimulation of immune cells tales places in secondary lymphoid organs like the lymph nodes
and spleen. Briefly, the theory focuses on explaining the mechanism involved during the
production of the various type of the antibody. We have four postulates that summarize the ideas
of clonal selection theory which include: that those immune cells bearing receptor for self-
molecules are likely to be damaged at an early stage.

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Additionally, receptor occupation is needed for cell stimulation, and every lymphocyte has a
single type receptor with distinctive specificity. The differentiated effector cells resulting from a
stimulated lymphocyte will have receptor of identical specificity as the mother cell.
Immunological memory is a key feature of both invertebrate and vertebrate immune system. It is
potential of the immune system to recall, recognize and react very fast and effectively to a
pathogen which has been met before. Immunological memory offers protection from recurring
infection and establishes natural immunity against infection (Pantoja, Paine, and Vallejo-Marín,
2018).
The clonal selection brings about amplification and differentiation of lymphocytes that are
antigen-specific into effector cells and memory cells. Memory cells can even live for a lifetime,
and we have immunological memory in both humoral and cellular immunity. Autoimmunity is a
system of the immune response of the host against its healthy cells and tissues. Diseases resulting
from such response are mostly treated using steroids.
The knowledge of the autoimmunity has been emphasized over the past 50 years to examine the
formation of forbidden clones that results from either mutation or other bad condition in the
body. Burnet’s concepts of mutagenesis as a fundamental element of various pathologies
involving autoimmunity is offered the current focus. Clonal selection theory is so correct since it
has facilitated to more understanding of the autoimmunity via several experimental proves.
Conclusion
The assessment has covered all the task in a precise manner that a person can read and
understand the targeted concept. It has coven pathogen, and it types, resident flora, blood clotting
process, types of immunity, the concept of antibody and antigen and clonal selection theory.

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Biology course in nursing is very vital as it exposes nurses in important areas to enhance
competence in the nursing profession.
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