• A. B lymphocytes
  • B. Phagocytic cells
  • C. Complement system
  • D. T lymphocytes ✓


When an individual becomes infected with Pneumocystis jiroveci, it typically suggests a defect in T lymphocytes within the immune system. Pneumocystis jiroveci is an opportunistic fungal pathogen that can cause severe pneumonia, particularly in individuals with weakened immune systems. Here’s why a defect in T lymphocytes is implicated:

  1. Role of T Lymphocytes: T lymphocytes, also known as T cells, are a type of white blood cell that plays a crucial role in the adaptive immune response. They are responsible for recognizing specific antigens and coordinating the immune response against pathogens like bacteria, viruses, and fungi.
  2. Cell-Mediated Immunity: T lymphocytes are essential for cell-mediated immunity, which involves the activation of various types of immune cells to directly attack and destroy infected cells or pathogens. In the case of Pneumocystis jiroveci infection, T lymphocytes are critical for recognizing and responding to the fungus to prevent its proliferation and spread.
  3. Deficiency in T Lymphocytes: When there is a defect or deficiency in T lymphocytes, the body’s ability to mount an effective immune response against pathogens is compromised. This can lead to an increased susceptibility to opportunistic infections like Pneumocystis jiroveci pneumonia, especially in individuals with conditions that affect T cell function, such as HIV/AIDS or certain immunodeficiency disorders.
  4. Clinical Implications: In clinical practice, the presence of Pneumocystis jiroveci infection often prompts healthcare providers to investigate the patient’s immune status, particularly focusing on T cell function. Testing for T cell counts and activity may be necessary to assess the underlying immune deficiency that predisposed the individual to the infection.

In summary, infection with Pneumocystis jiroveci suggests a defect in T lymphocytes, highlighting the importance of these immune cells in protecting against opportunistic pathogens and maintaining overall immune function.

In other words, infection with Pneumocystis jiroveci, a fungus causing pneumonia in immunocompromised individuals, suggests a defect in T lymphocytes. Pneumocystis jiroveci pneumonia (PJP) is commonly seen in individuals with weakened immune systems, such as those with HIV/AIDS or undergoing immunosuppressive therapy. T lymphocytes play a crucial role in coordinating the immune response against pathogens like Pneumocystis jiroveci. A deficiency in T lymphocytes can impair the body’s ability to mount an effective immune response against this opportunistic pathogen, leading to increased susceptibility to PJP.

B lymphocytes primarily produce antibodies that target specific pathogens, while phagocytic cells are responsible for engulfing and destroying foreign invaders. The complement system consists of proteins that enhance the body’s ability to fight infections through various mechanisms. However, in the case of Pneumocystis jiroveci infection, the defect lies more prominently in T lymphocytes due to their critical role in orchestrating the immune response against this particular pathogen.

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