An immunologist is a scientist who studies the immune system, which is the body's defense mechanism against infections and diseases. They investigate how the body recognizes and responds to harmful substances, such as bacteria, viruses, and allergens. Their work helps in understanding various immune-related conditions, including allergies, autoimmune diseases, and immunodeficiencies. Immunologists often conduct research to develop vaccines and treatments that enhance or modify the immune response. They may work in laboratories, hospitals, or academic institutions, collaborating with other healthcare professionals, such as microbiologists and pharmacologists, to improve public health outcomes.