Understanding Immunodeficiencies, AIDS, and HIV

Immunodeficiencies: Types and Causes

An individual suffers from an immunodeficiency when their immune system is unable to effectively combat or stop an infection. These conditions are broadly categorized into two main types: congenital and acquired.

Congenital Immunodeficiencies

Congenital immunodeficiencies are genetic and inherited conditions. They arise from failures in the synthesis of the complement system or from the abnormal development of lymphoid organs. These can manifest as:

• B Lymphocyte Defects

  These are due to defects in B lymphocytes, which are unable to produce normal antibodies or produce them in insufficient quantities. Symptoms typically do not appear until after 6 months of age.

• T Lymphocyte Defects

  Defects in T lymphocytes are generally more serious. Patients with T lymphocyte failures frequently experience latent viral infections such as chickenpox and herpes, as well as various fungal infections and tuberculosis.

Acquired Immunodeficiencies

Acquired immunodeficiencies can appear at any point in life. They are caused by various external factors and are not due to genetic defects.

AIDS: Acquired Immune Deficiency Syndrome

AIDS (Acquired Immune Deficiency Syndrome) is an infectious disease that progressively diminishes the immune response, ultimately leading to its destruction. It is characterized as an acquired cellular immunodeficiency.

Understanding HIV: The Cause of AIDS

The Human Immunodeficiency Virus (HIV) is the causative agent of AIDS. HIV belongs to the family of retroviruses. Its genetic material is RNA, and it copies this genetic information into DNA using the enzyme reverse transcriptase. This enzyme has no error correction mechanism, which allows the virus to constantly mutate, making it challenging to treat.

HIV Transmission Routes

The HIV virus is contagious and can be transmitted through various forms of contact:

• Blood-to-Blood Contact: For example, among individuals sharing needles.
• Sexual Fluids and Blood Contact: Such as through unprotected sexual intercourse.
• Mother-to-Child Transmission: The virus can cross the placenta and reach the fetal bloodstream during pregnancy, or be transmitted during childbirth or breastfeeding.

Stages of HIV Infection

Upon entry into the body, the Human Immunodeficiency Virus (HIV) may initially cause no symptoms or only very mild ones.

Initial Symptoms and Seroconversion

Approximately three months after infection, specific antibodies become detectable in the bloodstream. This event is known as seroconversion, indicating a seropositive individual. The virus primarily infects cells such as T lymphocytes, leading to a decrease in their number. At this early stage, the individual's quality of life may not be immediately affected.

Progression to Opportunistic Infections

Over time, the number of T lymphocytes begins to decline significantly. This reduction triggers an increased risk for certain diseases, known as opportunistic infections, which include conditions like pneumonia and meningitis.

Advanced HIV and Treatment

In advanced stages, the T lymphocyte count can drop below 200 lymphocytes per mm³ of blood. At this critical level, the immune system is severely compromised, making the individual highly susceptible to severe opportunistic infections, such as Pneumocystis carinii pneumonia, or the development of various sarcomas. Today, HIV infection is largely controlled through the use of antiretroviral therapies (ART). However, prevention remains the most effective weapon against this disease.