Quiz حول الأنتيجينات والجهاز المناعي

Antigen and Immunogen

• Antigen: Any foreign substance that triggers an immune response.
• Immunogen: An antigen with the specific characteristics to stimulate an immune response.
• Immune response: The reaction of the immune system to an immunogen.
• Immunogen properties:
  • Molecular weight greater than 10 kDa is ideal.
  • Complex structure (e.g., microorganism, not just epitopes).
  • Non-self (foreign). The greater the difference from human-derived antigens, the better the response.
  • Accessible.
• Route of antigen entry into the body is also important.

Immune System Functions

• Beneficial:
  • Prevents the entry of foreign agents.
  • Prevents the growth of cancerous cells.
• Potential Harm:
  • In cases like COVID-19, the body's overreaction can lead to damage. Instead of 5,000 immune cells, only 500 might be present in parts of the respiratory system. This can cause respiratory failure.

Allergies

• Reduced tolerance to self-cells.

Cancer

• The immune system's ability to fight cancer can weaken over time.

Edward Jenner

• Jenner, considered the "father of immunology," observed that milkmaids rarely contracted smallpox.
• Jenner's study and vaccination using cowpox led to the development of smallpox vaccinations.

Types of Granulocytes

• Neutrophils
• Eosinophils
• Basophils
• Mast cells (mastocytes)
• Platelets (derived from megakaryocytes)

Innate Immunity

• Present from birth, no prior training needed.
• Rapid response to antigens.
• Mechanisms include skin barriers, responses to acidic environments, normal flora on skin, reflexes like sneezing and coughing, urinary reflexes and eye reflexes.

Adaptive Immunity

• Resistance acquired by the body against foreign agents.
• Can become long-lasting and lead to immunological memory.

Dendritic Cells (DCs)

• Professional antigen-presenting cells (APCs).
• Primarily reside in tissues, especially skin and mucosal surfaces.
• Important link between innate and adaptive immunity.

Natural Killer (NK) cells

• Derived from lymphoid lineage and have characteristics similar to lymphocytes.
• Functions:
  • Destroy cancer cells.
  • Destroy virus-infected cells.
  • Signal for activation of other immune cells
• NK cell killing: Releasing perforin to create pores in the target cell membrane (allowing entry of granzymes) leading to programmed cell death (apoptosis).

Basophils and Mast Cells

• Both release histamine and other inflammatory mediators.
• Basophils are in the blood; mast cells are primarily found in tissues.

Other immune cells:

• Monocytes
• Macrophages

Antigen Presentation (APC)

• APCs engulf antigens, digest them, and present fragments on their surface.
• These fragments are recognized by T cells.
• Neutrophils are not APCs but play a role in digestion and presenting.

Complement System

• Various functions, including:
  • Tagging foreign cells for destruction.
  • Promoting inflammation.
• Activation pathways:
  • Classical
  • Alternative
  • Lectin
• Control mechanisms:
  • Inhibitors present to prevent uncontrolled activation.
• Disorders:
  • Deficiencies can increase susceptibility to infections.

Immunoglobulins (Antibodies)

• Structure:
  • Heavy chains
  • Light chains
  • Constant region (Fc)
  • Variable region (Fab)
  • Hinge region
• Function:

Types of Immunoglobulins (Antibodies)

• IgG
• IgA
• IgM
• IgE
• IgD

Factors influencing Ab reactions:

• Temperature (e.g., cold vs. warm reacting antibodies).
• pH.
• Ag concentration
• Affinity, specificity

Antibody-Mediated Immunity (Humoral Immunity)

• B cells produce antibodies.

Antigen-Dependent vs. Antigen-Independent Response

• Antigen-Dependent (cells require initial T-cell help)
  • Production of memory cells. Response is more intense and faster in subsequent reactions.
• Antigen-Independent
  • Ig(M) is often the primary antibody response.
  • Limited memory cells produced.

Immune System Response Phases

• Primary Immune Response
• Secondary Immune Response (class switching)

Immunological Tests

• Various tests, e.g., ELISA, blood tests, skin tests, for diagnosing and monitoring various immune responses.

Immune System Disorders

• Primary immunodeficiencies:
• Secondary (acquired) immunodeficiencies: