Microbiology and Immunology

Posted on Oct 27, 2024 in Biology

Anthrax

Anthrax is a highly aggressive bacterial disease that can be fatal. Used as a biological weapon, it persists in the ground (reservoir), affecting sheep and other grazing animals. The bacteria form spores with a tough outer covering.

Viruses

Features

Viruses are macromolecules with a protein coat containing a single type of nucleic acid, either DNA (like adenoviruses) or RNA (like retroviruses). As obligate parasites, they use the genetic material of the cells they infect. Viruses can infect bacteria, plants, animals, and humans. They are not controlled by antibiotics; existing drugs only reduce symptoms due to the viruses’ constant mutation. Viruses are not considered living cells but rather a link between living and non-living matter.

Viral Diseases

  • Colds
  • Influenza
  • Measles
  • Herpes
  • Warts
  • AIDS
  • Infectious Hepatitis
  • Rubella
  • Mononucleosis
  • Chickenpox
  • Rabies
  • Mumps
  • Poliomyelitis
  • Smallpox
  • Condylomata
  • AH1N1
  • Hanta Virus
  • Avian Influenza

Symptoms of Viral Diseases

  • Fever
  • Headache
  • Chills
  • Muscle pain
  • Nausea
  • Vomiting
  • Rhinorrhea
  • Diarrhea

Bacteriophage

A bacteriophage is a virus that infects bacteria. It operates via two pathways: the lytic pathway, where the virus activates its genetic material to destroy the bacteria and replicate viral particles, or the lysogenic pathway, where the viral genetic material integrates into the bacterial genetic material. In the lysogenic pathway, the viral genetic material is called a prophage. When duplicated outside the host cell without forming a capsule, the virus is called a virion.

Prions

Prions are protein molecules that can alter cell material, such as in mad cow disease.

Stages of Viral Duplication (Retroviruses (RNA) or Adenoviruses (DNA))

  1. Penetration: The virus enters the host cell (endocytosis). Some viruses have surface proteins that bind to receptors on the cell membrane, stimulating endocytosis. The viral genetic material is released into the cytoplasm.
  2. Duplication: The viral genetic material is copied multiple times.
  3. Transcription: Viral genetic material is used as a template to produce messenger RNA (mRNA).
  4. Protein Synthesis: In the host cell’s cytoplasm, viral mRNA is used to synthesize viral proteins.
  5. Viral Assembly: The genetic material and enzymes are encased in viral proteins.
  6. Liberation: New viruses exit the cell by budding from the cell membrane or by cell rupture.

Antigens

Antigens are specific proteins found on the surface of pathogens or on the surface of bacteria. Their presence is detected by red blood cells and determines blood type. During infection, viral or bacterial antigens are found in blood plasma and produce different diseases. The ELISA test detects the presence of the antigen in plasma (e.g., for HIV). Sometimes, the virus affects the host in a developed or terminal stage.

AIDS (Acquired Immunodeficiency Syndrome)

AIDS is caused by the HIV retrovirus. Symptoms are triggered by the impact of HIV in its terminal stage.

Spread of AIDS

  • Contaminated blood transfusions
  • Sexual contact with an infected person
  • Sexual promiscuity
  • Contaminated breast milk
  • Transmission during pregnancy
  • Use of contaminated toothbrushes (gingivitis)
  • Contaminated razor blades
  • Drugs made from contaminated blood

HIV+

Individuals who are HIV+ have the antigen in their body and can develop the disease. They may be asymptomatic. Within a period of 10 years from the onset, death can occur. Treatment involves triple therapy, which doesn’t eliminate the virus but reduces symptoms. In some asymptomatic cases, individuals can live beyond 10 years after infection (carriers). HIV weakens the body’s immune system, leading to death from opportunistic infections. HIV affects white blood cells (normal range: 6,000-8,000/µL of blood; in the terminal stage, it can drop to 200/µL).

White Blood Cells

White blood cells are produced in the red bone marrow, tonsils, thymus, spleen, and appendix. They exhibit diapedesis, positive chemotaxis, pseudopod formation, and phagocytosis. Types affected by HIV (AIDS) include helper T cells (CD4) and cytotoxic T cells (CD8). They have different lifespans (days, months, years) and vary in size (5-20 microns in diameter, e.g., macrophages).

Types of White Blood Cells

  • Granular: Neutrophils, Basophils, Eosinophils
  • Agranular: Monocytes, Macrophages, Lymphocytes (B cells and T cells)

Agranular white blood cells: Monocytes mature into macrophages (larger size). Macrophages and neutrophils are the primary phagocytes, engulfing and destroying foreign substances or infected cells. Lymphocytes are the first line of defense, providing humoral immunity through specific proteins released into blood plasma to neutralize antigens.

B Lymphocytes

B lymphocytes are responsible for humoral immunity by secreting antibodies that act on pathogens. They can act in the blood plasma. The forms of action on pathogens include:

  • Antitoxins: Inhibit or block the action of toxins.
  • Agglutinins: Cause agglutination of pathogens to prevent their spread.
  • Precipitins: Cause precipitation of pathogens, reducing their spread.
  • Opsonins: Weaken or perforate pathogen membranes using the enzyme perforin, facilitating destruction by macrophages or natural killer cells.
  • Cytolysins: Destroy cells.
  • Memory B cells: Produce antibodies that remain in the blood plasma, allowing the body to recognize and react to a second infection by the same pathogen, facilitating a faster immune response.

T Lymphocytes

T lymphocytes mature in the thymus and provide cellular immunity, killing infected cells through direct contact. They are classified into: Helper T cells (CD4), Cytotoxic T cells (CD8), Suppressor T cells, Memory T cells, and Natural Killer (NK) cells.

Kaposi’s Sarcoma

Stages: 1. Acute (3 months) / 2. Chronic (6-8 years) / 3. AIDS (2 years)

Blood Serum

Zero +: Rh+ / Zero -: Rh-

Defensive Barriers

  • Skin: The main physical barrier, with pores, sweat, and hair, releasing toxins and regulating body temperature.
  • Hairs: Filter germs and dust.
  • Mucus: Traps impurities and pathogens, especially in the respiratory and gastrointestinal tracts.
  • Cilia: Trap and remove foreign substances in the respiratory and genital tracts.
  • Saliva and Urine: Contain lysozyme, which is bactericidal and acts as a lubricant.
  • Stool: Eliminates microflora.
  • Vomiting: A defensive mechanism that eliminates foreign substances and microorganisms.
  • Acidic pH of the skin
  • Digestive juices
  • Interferons
  • Fever: Inhibits the growth of microorganisms and speeds up recovery.
  • Inflammation: Destroys microbes, limits their spread, and repairs tissues.
  • White blood cells