In the setting of HIV, what does a CD4 count of less than 200 indicate?

A CD4 count of less than 200 cells/mm³ in a patient with HIV indicates a significantly compromised immune system, categorizing the individual as having AIDS (Acquired Immunodeficiency Syndrome). The CD4 cell count is a crucial marker of immune function in HIV-infected individuals, as CD4 cells are critical for orchestrating the immune response.

When the CD4 count falls below this threshold, the patient is at a much higher risk for opportunistic infections. This is due to the diminished ability of the immune system to respond to pathogens, particularly those that a healthy immune system would normally easily control. Opportunistic infections can include severe forms of pneumonia, certain types of cancer, and infections from organisms such as Toxoplasma or Mycobacterium avium complex, which would not typically pose a threat to individuals with healthy immune systems.

The other options do not correctly reflect the implications of a CD4 count below 200. A low viral load is associated with effective treatment, but a low CD4 count indicates the opposite in terms of immune health. An increased immune response would suggest a healthier immune system capable of fighting infections, which is not the case here, and a normal immune system would not be indicated with such a low CD4 count