Chamberlain College of Nursing
NR 507 - Advanced Pathophysiology (2024-2025)
Edapt – Week 1 Immune Response (3 Modules)
Modules: Hypersensitivity, Immunodeficiency, and Autoimmunity
Hypersensitivity:
Hypersensitivity Reactions
The immune system functions to eliminate pathogens from the body using various mechanisms.
A pathogen is just simply a bacterium, virus or other microorganism that can cause disease.
These mechanisms typically create a localized inflammatory response that effectively eliminates
the pathogen without minimal damage to the surrounding tissue. Besides pathogens,
individuals come into contact with numerous foreign antigens, such as plant pollen and food.
Contact with these environmental antigens does not elicit an immune response in the majority
of individuals. However, in certain predisposed individuals, the immune system can mount a
response to these generally innocuous antigens, resulting in tissue damage that ranges from
mild irritation to life-threatening anaphylactic shock. These immune responses are referred to
as allergic reactions or hypersensitivity reactions. Hypersensitivity reactions can be divided into
four categories, Type I to Type IV, distinguished by the cell types and effector molecules
involved.
Immune System
Which of the following are considered the “first responders” of the innate immune system?
Neutrophils.
IgM.
T-cells.
Eosinophils.
Feedback:
Neutrophils appear first in any immune response.
Hives
Hives (urticaria) are an example of a:
Type 1 hypersensitivity reaction.
Type 2 hypersensitivity reaction.
Type 3 hypersensitivity reaction.
Type 4 hypersensitivity reaction.
Feedback:
Hives (urticarial) are an example of a Type 1 hypersensitivity reaction mediated by the antibody,
IgE and mast cells.
Type 2 Hypersensitivity Reactions
Type 2 (Cytotoxic) hypersensitivity reactions are mediated by:
,IgE or IgG.
IgG or IgM.
IgM or IgA.
IgA or IgE.
Feedback:
The Type 2 hypersensitivity reaction is mediated by IgG or IgM.
Contact Dermatitis
Allergic contact dermatitis is an example of
Type 4 hypersensitivity reaction.
Feedback:
Allergic contact dermatitis is an example of a Type IV hypersensitivity reaction mediated by T-
cells. When the individual comes in contact with the antigen (e.g. poison ivy), an antigen
complex is formed. On subsequent exposure to the antigen, sensitized T-cells activate the
inflammatory process that causes the allergic contact dermatitis to appear.
Anaphylaxis
Anaphylaxis is a Type 1 hypersensitivity reaction.
Feedback:
Type 1 hypersensitivity reactions are mediated by IgE and mast cells. An individual who is highly
sensitized to the antigen may experience anaphylaxis.
Type I: Allergic Reaction
On initial encounter with an allergen, the individual will first produce IgE antibodies. After the
allergen is cleared, the remaining IgE molecules will be bound by mast cells, basophils, and
eosinophils that contain receptors for the IgE molecules. This process is referred to as
sensitization. On subsequent exposure to the allergen, the IgE molecules located on the
sensitized cells induces their immediate degranulation. This causes the release of inflammatory
mediators such as histamine, leukotrienes, and prostaglandins that results in vasodilation,
bronchial smooth muscle contraction, and mucus production. Type I hypersensitivity reactions
can be local or systemic. Systemic reactions can result in anaphylaxis, a potentially life-
threatening condition. Allergic asthma is an example of a Type I hypersensitivity reaction. On
exposure to certain allergens (typically inhaled), individuals with allergic asthma experience
inflammation of the airways, characterized by tissue swelling and excessive mucus production.
This narrowing of the airways makes it difficult to breathe.
Allergic Asthma
Review the clinical application of allergic asthma below.
J.S. is a 64-year old female who presents to the primary care office with complaints of low back
pain and burning on urination. She also indicates that she has been urinating frequently and has
,had to wear a pad because she also is experiencing urgency and she is afraid that she might
“leak”. She tells the Nurse Practitioner (NP) that she suspects that she has a urinary tract
infection (UTI). She reported that it has been at least 2 years since she had a UTI and was
treated with an antibiotic but cannot remember its name. She denies any medication or food
allergies. After conducting a thorough health history and physical exam, the NP diagnoses the
patient with uncomplicated UTI and orders a course of sulfamethoxazole/trimethoprim
(Bactrim DS).
The next day, J.S. returns to the office in a panic to report she has just taken her first dose of
the medication about an hour ago. She began to feel anxious followed by wheezing in the chest
and dizziness. She first called her daughter, who reminded her that she is allergic to sulfa
drugs. J.S. is immediately examined by the NP. The subjective and objective findings are:
Subjective:
Anxious
Dizziness
Wheezing
Objective:
Vital signs: BP 90/50, HR 112
Red rash on chest and anterior neck
Swelling around the right eye
Wheezing with airflow throughout lung fields
When analyzing patient symptoms, the nurse practitioner (NP) relies on pathophysiology to
explain the cause of the symptoms. Once the underlying reasons for the symptoms are
identified, the NP can make an accurate diagnosis and select appropriate treatment.
Note that our patient is experiencing both localized symptoms (rash on chest and anterior neck
and right eye swelling) and systemic symptoms (wheezing and hypotension).
Let’s use our knowledge of pathophysiology to explain why she is having these presenting
symptoms.
The NP quickly identifies this as an allergic reaction and immediately asks the patient again, if
she is aware of any prior allergies to medications. The patient tells the NP that her daughter
reminded her that she is allergic to sulfa drugs. The Bactrim, in this case, is considered the
allergen to which the patient has become sensitized from the last time she was treated for a
UTI.
At the time that she became sensitized, the IgE antibodies attached to the cells that became
sensitized and then at the time of further exposure, IgE caused the sensitized cells to
, degranulate. When degranulation occurs, inflammatory mediators like histamine, leukotrienes
and prostaglandins are released to produce several effects on the body. Vasodilation occurs
which explains the patient’s hypotension, dizziness and rash).
At this point, inflammatory mediators are released. These include histamine, leukotrienes, and
prostaglandins. Constriction of bronchial smooth muscle also occurs, which explains her
respiratory symptom of wheezing. Based on the localized and systemic symptoms, the NP can
diagnose the patient with anaphylactic reaction, a Type 1 hypersensitivity reaction.
Type II Hypersensitivity Reaction
A Type II hypersensitivity reaction is tissue-specific and usually occurs as a result of haptens that
cause an IgG antibody or IgM antibody mediated response. The antibodies are specifically
directed to the antigen located on the cell membrane. A hapten is a small molecule that can
cause an immune response when it attaches to a protein. Macrophages are the primary
effector cells of Type II responses. Typical examples of Type II reactions are drug allergies, as
well as allergies against infectious agents.
The Type II response begins with the antibody binding to the antigen and may cause the
following:
The cell to be destroyed by the antibody
Cell destruction through phagocytosis by macrophages
Damage to the cell by neutrophils triggering phagocytosis
Natural killer cells to release toxic substances that destroy the target cell
Malfunction of the cell without destruction
Examples of type II reactions include drug allergies, hemolytic anemia, blood transfusion
mismatch with resulting transfusion reaction and Rh hemolytic disease.
Delayed Hemolytic Transfusion Reaction
Review the clinical application of Delayed Hemolytic Transfusion reaction below.
M.G., a 27-year old healthy female required a blood transfusion 4 hours post-partum after
undergoing a C-section. Twenty-four hours later, she and her newborn were released from the
hospital in good health. Approximately 1 week later, she came to the primary care office
complaining of fever, chills, shortness of breath (dyspnea) and a backache.
The NP conducts an exam and the subjective and objective findings reveal the following:
Subjective:
Fever
Chills
Shortness of breath (dyspnea)
