Foreign Invaders and Immune Responses

How does the immune system protect the body from disease? The immune system employs various strategies to combat foreign invaders and maintain homeostasis.

Types of foreign invaders:

1. Pathogens: Viruses, bacteria, or other living organisms that cause disease or immune responses
2. Antigens: Toxins produced by pathogens that harm the organism and are recognized as foreign by the immune system

Vocabulary: Lymphocytes are white blood cells that target invaders by producing proteins called antibodies.

How does the body react to infection? The body employs two main types of immune responses:

1. Nonspecific Immune Response (Innate Immunity):

   • Physical and chemical barriers: Skin, tears, mucus, cilia, stomach acid, urine flow, and "friendly" bacteria
   • Fever: Elevated body temperature to denature invaders' proteins

2. Specific Immune Response (Adaptive Immunity):

   • Targets specific pathogens or antigens
   • Involves the creation of antibodies by B-cells (a type of white blood cell)

Example: Fever is an example of a nonspecific immune response where the high temperature kills invaders by denaturing their proteins.

Types of immunity:

1. Active Immunity: Body creates antibodies through immune response (via sickness or immunization)
2. Passive Immunity: Antibodies received from an external source (e.g., mother to child at birth or through breast milk)

Highlight: The immune system's response to pathogens and antigens is another example of homeostasis in action, maintaining the body's dynamic equilibrium.

Immune System Components and Disease

The immune system comprises various components that work together to protect the body from disease and maintain homeostasis.

Key components of the immune system:

1. Antibodies: Proteins produced by the immune system to fight antigens
2. White blood cells: Attack pathogens, produce antibodies, and remember pathogens
3. Memory cells: A type of white blood cell that remembers antigens for faster future responses

Definition: Disease is a failure of homeostasis in the body.

Specific roles of immune cells:

• T-cells: Recognize viral antigens outside infected cells
• B-cells: Recognize surface antigens of bacteria and viruses, attack invaders outside the cell

Human Immunodeficiency Virus (HIV) and the immune system:

• HIV attacks white blood cells, specifically T-cells
• The virus mutates rapidly, making it difficult for the body to create effective antibodies
• HIV can develop into AIDS (Acquired Immunodeficiency Syndrome)

Highlight: HIV invades T-cells, copies itself inside the host cell, and ultimately destroys it, severely compromising the immune system.

Importance of protein structure in immune function:

In proteins, shape determines function. This principle applies to:

• Hormones
• Enzymes
• Antibodies
• Receptors

Understanding these components and their interactions is crucial for comprehending how the immune system fights viruses and maintains overall health.