The Immune System

Running head: IMMUNE SYSTEM 1
The Immune System
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IMMUNE SYSTEM 2
The Immune System
The immune system is necessary for human survival in the vast environment full of
pathogens. The human body would be susceptible to infectious diseases in the absence of an
immune system. It is crucial in fighting off pathogens, such as viruses and bacteria that often
cause infections. It comprises various immune cells that together work to mount an
immunological response against invaders. Notably, the innate (non-specific) and adaptive
(acquired) immune systems scavenge dead cells, destroy malignant cells, and protect the body
from pathogens via various mechanisms. Not only does the immune system fight infections but
also crucial in mounting immunological effects during healing processes.
Types of Immune Systems
Innate (Non-specific) Immunity
Innate immunity is quick and effective. A person inherits the non-specific immunity from
parents. Its non-specificity is elicited from its response against various invaders. Innate immunity
serves as a barrier to the entry of pathogens via the external and internal surfaces. For instance, it
destroys within a short period the bacteria that tries to enter the skin through a wound. The
natural immunity comprises of the skin, mucosal lining, leukocytes, and other components of
body fluids. The skin and mucosal lining offer protection from the outside. They act as
mechanical barriers; hence, preventing the entry of invaders (Thompson, 2015). More also,
saliva and tears have lysozyme that elicits digestive properties which render antigens mild.
Additionally, the movements by cilia and gastrointestinal muscles prevent the adherence of
pathogens to membranes. The mucosal lining secretes mucus that traps and immobilizes
pathogens. Besides, the human body temperature and vaginal secretions create an unfavorable
environment for microbes to thrive.

IMMUNE SYSTEM 3
However, the passage of pathogens through the physical barriers trigger the second line
of defense mechanisms. It recruits cells to the site of infection. Typically, the hematopoietic stem
cells differentiate into myeloid progenitor cells that synthesize various leucocytes, for instance,
macrophages, monocytes, neutrophils, natural killer cells, dendritic cells, eosinophils, and
basophils. Notably, phagocytic leucocytes have pattern recognition receptors (PRRs) which
recognizes particular pathogen-associated molecular patterns (PAMPs) (Plato, Hardison &
Gordon, 2015). If invaders enter the body, dendritic cells present on the skin and lymph nodes
ingest and process the exogenous antigens for easier presentation to T-lymphocytes by Major
Histocompatibility Complex (MHC) II (Nicholson, 2016). Also, innate immune systems release
natural killer cells that adhere to viruses and secrete cytokines that lyse viral components.
Besides, the freely circulating eosinophils adhere, poke holes, and ingest pathogens that
are too large for other phagocytes to digest. According to Iwasaki and Medzhitov (2015), the
innate immune system elicits its response by phagocytosis; pathogens adhere to the phagocytic
cells whose membranes extend to surround the invader. The phagocytes take the microbe into a
vesicle with lysosomes that process the pathogens into antigenic fragments, which are presented
to T-lymphocytes. Activated T-lymphocytes trigger the release of cytokines and interleukin 2
that destroy the antigens. More also, it activates the complement system; it comprises of several
proteins that work to eliminate infectious pathogens (Merle et al., 2015). The system marks
invaders; attract phagocytic cells; dissolve bacterial cell walls; lyse viruses. As a result,
inflammation ensues due to infiltration of phagocytes into the site of invasion. Inflammatory
response results in redness, pain, and fever (Vincenzo et al., 2015).
Adaptive (Acquired) Immunity