Immunity, Infections, Inflammation, Blood and Lymphatics

Innate vs. Acquired Immunity

• Innate Immunity: The body's first line of defense, present at birth, responds quickly and non-specifically to pathogens. Includes physical barriers like skin and mucous membranes, and immune cells like phagocytes.
• Acquired (Adaptive) Immunity: Develops after exposure to specific antigens, slower but highly specific. Involves lymphocytes (B and T cells), has memory and provides long-term protection.

Lines of Defense

• First Line: Physical, mechanical, and biochemical barriers like skin and mucous membranes.
• Second Line: Inflammation - a rapid response to injury or infection involving immune cells like neutrophils and macrophages.
• Third Line: Adaptive immunity involving lymphocytes (B and T cells) and the production of antibodies.

Inflammation Process

• Stages:
  • Vasodilation: Increased blood flow to the area.
  • Increased vascular permeability: Fluid and immune cells leak from blood vessels into the tissues.
  • White blood cell migration: Phagocytes engulf and destroy pathogens.
• Signs: Redness, heat, swelling, pain, and loss of function.

Wound Healing

• Primary Intention: Minimal tissue loss, wound edges are approximated, heals quickly with minimal scarring.
• Secondary Intention: More extensive tissue loss, heals from the bottom up with more tissue replacement and a higher chance of scarring.

Factors Inhibiting Wound Healing

• Ischemia (lack of oxygen)
• Excessive bleeding
• Obesity
• Diabetes
• Wound infection
• Tobacco use
• Age

Pediatric and Geriatric Considerations in Wound Healing

• Pediatric: Newborns rely on maternal antibodies for immunity and have underdeveloped immune responses.
• Geriatric: Older adults may have impaired healing due to chronic illnesses, reduced immune function, and medications.

Adaptive Immunity

• Primary Response: Initial exposure to an antigen, takes about 7-14 days to produce antibodies (IgM first, then IgG).
• Secondary Response: Memory cells quickly recognize the antigen, producing a faster and stronger response (predominantly IgG).

Factors Influencing Infection

• Communicability: Ability to spread from one individual to another.
• Infectivity: Ability to invade and multiply in a host.
• Virulence: Severity of the disease caused by the pathogen.
• Pathogenicity: Ability of an organism to cause disease.

Active Immunity

• Results from exposure to an antigen (through infection or vaccination) leading to the production of specific antibodies.

HIV/AIDS

• HIV: Infects and destroys CD4+ T-helper cells, impairing both humoral and cell-mediated immune responses.
• AIDS: The progression of HIV, marked by a severe decline in immune function, leaving the body vulnerable to opportunistic infections.

Hypersensitivity

• Type I: IgE-mediated, common in allergies.
• Type II: Tissue-specific reactions, e.g., blood transfusion reactions
• Type III: Immune complex-mediated, as in lupus.
• Type IV: Cell-mediated, like poison ivy reactions.

Autoimmunity

• The immune system mistakenly attacks the body’s own tissues, as seen in diseases like lupus.

Lupus

• A chronic autoimmune disease characterized by a variety of symptoms, including the signature butterfly rash, joint pain, and systemic inflammation.

Transfusion Reactions

• Occur when there is an immune response to transfused blood due to mismatched blood types (e.g., ABO or Rh incompatibilities). Symptoms may include fever, chills, shortness of breath, and low blood pressure.

Transplant Rejection

• The immune system attacks the transplanted organ:
  • Hyperacute rejection: Immediate reaction due to pre-existing antibodies.
  • Acute rejection: Occurs within weeks to months of transplantation.
  • Chronic rejection: Develops over months or years, leading to gradual organ damage.

Stress and the Body's Response

• The HPA axis is activated during stress, leading to the release of cortisol, which elevates blood glucose and suppresses the immune response.
• Chronic stress is linked to several health issues, including cardiovascular diseases and immune suppression.

Immunity and Stress

• Stress can lower immune function by reducing T-cell cytotoxicity and B-cell responses, increasing susceptibility to infections and diseases.

Test your knowledge on innate and acquired immunity! This quiz covers the body's lines of defense, the inflammation process, and the specifics of immune responses. Understand how innate immunity functions as the first line of defense and how acquired immunity develops over time.