PHA 046 Pharmaceutical Microbiology and Parasitology -BASIC IMMUNOLOGY, Study Guides, Projects, Research of Pharmaceutical Microbiology

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Introduction to Basic Immunology

LEARNING OUTCOME

1. Define basic Immunology

2. Describe the general and specific defense

mechanism.

3. Differentiate the general and specific defense

mechanisms.

4. Discuss Immunization and Immune Testing

5. Discuss disorders that can be broadly categorized into

immunodeficiency diseases, autoimmune diseases, and

hypersensitivity reactions.

The immune system can be divided into two main components: innate immunity and adaptive immunity.

1. Innate Immunity

Innate immunity is the body's first line of defense against infections and is present from birth. It provides a rapid, non-specific response to pathogens and does not require previous exposure to the pathogen.

Key Components of Innate Immunity:

● Physical Barriers: ○ Skin: Acts as a physical barrier to prevent pathogen entry. ○ Mucous Membranes: Line the respiratory, gastrointestinal, and genitourinary tracts and trap pathogens. ● Cellular Defenses: ○ Phagocytes: Cells such as neutrophils and macrophages that engulf and destroy pathogens. ○ Natural Killer (NK) Cells: Lymphocytes that kill virus-infected cells and tumor cells. ● Molecular Defenses: ○ Cytokines: Signaling proteins that mediate and regulate immunity, inflammation, and hematopoiesis. ○ Complement System: A group of proteins that enhance phagocytosis, lyse pathogens, and stimulate inflammation. ● Inflammatory Response: ○ The body's response to injury or infection, characterized by redness, heat, swelling, and pain, which helps to isolate and eliminate pathogens and promote healing.

The immune system can be divided into two main components: innate immunity and adaptive immunity.

2. Adaptive Immunity

Adaptive immunity (or acquired immunity) is a specific immune response that develops after exposure to a

specific pathogen. It has two main characteristics: specificity and memory.

Key Components of Adaptive Immunity:

● Lymphocytes:

○ B Cells: Produce antibodies that bind to specific antigens (foreign substances) and neutralize or

mark them for destruction.

○ T Cells:

■ Helper T Cells (CD4+): Help activate B cells and other immune cells.

■ Cytotoxic T Cells (CD8+): Destroy virus-infected cells and tumor cells.

● Antibodies:

○ Proteins produced by B cells that specifically bind to antigens, leading to their neutralization or

destruction.

● Antigen-Presenting Cells (APCs):

○ Cells such as dendritic cells and macrophages that process and present antigens to T cells,

initiating the adaptive immune response.

The immune system can be divided into two main components: innate immunity

and adaptive immunity.

Types of Adaptive Immunity:

● Humoral Immunity: ○ Mediated by antibodies produced by B cells. It is effective against extracellular pathogens and toxins. ● Cell-Mediated Immunity: ○ Mediated by T cells. It is effective against intracellular pathogens (such as viruses) and cancer cells.

Immunological Memory:

One of the hallmarks of adaptive immunity is its ability to remember past infections,

leading to a more rapid and effective response upon re-exposure to the same

pathogen. This is the principle behind vaccination, where exposure to a harmless form

of a pathogen generates memory cells without causing disease, thus providing

protection against future infections.

Summary:

Immunology is fundamental to understanding how the body defends itself against

infections and other foreign substances. By distinguishing between innate and

adaptive immunity, we can appreciate the complexity and efficiency of the immune

system. This knowledge is crucial for developing vaccines, treatments for autoimmune

diseases, and therapies for allergies and immunodeficiencies.

Defense mechanisms of the body against pathogens can be broadly categorized into general (innate) and specific (adaptive) defense mechanisms. Here’s a detailed comparison:

General (Innate) Defense Mechanisms

Components:

1. Physical Barriers:

○ Skin: Acts as a physical barrier to block pathogen entry.

○ Mucous Membranes: Trap and remove pathogens in the respiratory, gastrointestinal, and

genitourinary tracts.

2. Chemical Barriers:

○ Lysozyme: An enzyme in saliva, tears, and mucus that breaks down bacterial cell walls.

○ Acidic pH: The low pH of the stomach and skin inhibits pathogen growth.

3. Cellular Defenses:

○ Phagocytes: Cells such as neutrophils and macrophages that engulf and destroy pathogens.

○ Natural Killer (NK) Cells: Lymphocytes that target and kill virus-infected and tumor cells.

4. Inflammatory Response:

○ Redness, heat, swelling, and pain that help isolate and eliminate pathogens and promote healing.

5. Complement System:

○ A group of proteins that enhance phagocytosis, lyse pathogens, and stimulate inflammation.

Defense mechanisms of the body against pathogens can be broadly categorized into general (innate) and specific (adaptive) defense mechanisms. Here’s a detailed comparison:

2. Specific (Adaptive) Defense Mechanisms

Definition: Adaptive defense mechanisms are specific and provide a second line of defense. They

develop after exposure to a specific pathogen and have a memory component.

Key Characteristics:

1. Specificity: ○ Adaptive immunity targets specific pathogens using specific receptors for antigens.
2. Delayed Response: ○ The response takes days to weeks to develop after the initial exposure to a pathogen.
3. Memory: ○ Adaptive immunity has a memory component that allows for a faster and more effective response upon subsequent exposures to the same pathogen.
4. Diverse and Flexible: ○ It can recognize and respond to a vast array of pathogens due to the diversity of antigen receptors on B and T cells.

Summary:

Innate immunity provides a rapid, non-specific response to

pathogens, forming the body's first line of defense, while

adaptive immunity offers a slower, highly specific response

with memory, forming the body's second line of defense.

Both systems work together to protect the body from

infections and ensure a robust and coordinated immune

response.

Immunization and Immune Testing

Immunization and immune testing are crucial aspects of modern medicine. They help in preventing diseases and diagnosing immune responses to various pathogens.

Immunization

Immunization is the process of inducing immunity to a specific disease by exposing the body to an antigen, usually through vaccination. This stimulates the immune system to produce a response that will protect against future infections.

Types of Immunization:

1. Active Immunization: ○ Natural Active Immunization: Occurs when a person is exposed to a live pathogen, develops the disease, and consequently builds a specific immune response. ○ Artificial Active Immunization: Achieved through vaccination, where an antigen (weakened or killed pathogen, or part of the pathogen) is introduced to stimulate the immune system without causing the disease.
2. Passive Immunization: ○ Natural Passive Immunization: Occurs naturally, such as the transfer of antibodies from mother to fetus through the placenta or from mother to baby through breast milk. ○ Artificial Passive Immunization: Involves the administration of pre-formed antibodies (immunoglobulins) from another individual or animal to provide immediate protection against a pathogen.

Types of Immunization:

1. Active Immunization: ○ Natural Active Immunization: Occurs when a person is exposed to a live pathogen, develops the disease, and consequently builds a specific immune response. ○ Artificial Active Immunization: Achieved through vaccination, where an antigen (weakened or killed pathogen, or part of the pathogen) is introduced to stimulate the immune system without causing the disease.
2. Passive Immunization: ○ Natural Passive Immunization: Occurs naturally, such as the transfer of antibodies from mother to fetus through the placenta or from mother to baby through breast milk. ○ Artificial Passive Immunization: Involves the administration of pre-formed antibodies (immunoglobulins) from another individual or animal to provide immediate protection against a pathogen.

Types of Immune Testing:

1. Serological Tests: ○ Detect antibodies or antigens in blood samples. ○ Examples: Enzyme-linked immunosorbent assay (ELISA), Western blot, Rapid diagnostic tests (RDTs).
2. Skin Tests: ○ Assess the presence of an immune response by introducing antigens into the skin. ○ Examples: Tuberculin skin test (Mantoux test), Allergy skin tests.
3. Cell-Mediated Immunity Tests: ○ Evaluate the function of T cells and other immune cells. ○ Examples: T-spot test, Lymphocyte proliferation test.
4. Flow Cytometry: ○ Analyzes the physical and chemical characteristics of cells in a sample. ○ Useful for identifying different types of immune cells and their states of activation.
5. Complete Blood Count (CBC) with Differential: ○ Measures the number and types of blood cells, including white blood cells (WBCs), which are crucial for the immune response.
6. Complement Activity Tests: ○ Assess the function of the complement system, a part of the innate immune response. ○ Examples: CH50 test, AH50 test.
7. Molecular Tests: ○ Detect the genetic material of pathogens. ○ Examples: Polymerase chain reaction (PCR), Real-time PCR (RT-PCR).

Importance of Immunization and Immune Testing:

● Disease Prevention: Vaccination is a primary method to prevent infectious diseases, reducing morbidity and mortality rates. ● Herd Immunity: Immunization helps achieve herd immunity, protecting those who cannot be vaccinated. ● Diagnosis and Monitoring: Immune testing aids in diagnosing infections, allergies, autoimmune diseases, and monitoring vaccine efficacy. ● Personalized Medicine: Understanding individual immune responses can lead to personalized treatment plans and better health outcomes.

Summary:

Immunization and immune testing are fundamental to maintaining public health and advancing medical

science. Vaccines prevent diseases by stimulating the immune system, while immune testing provides

insights into immune function and helps diagnose various conditions. Together, they play a critical role

in disease prevention, diagnosis, and management.