Biology STAAR (State of Texas Assessments of Academic Readiness) Practice Test

Which type of cells in the circulatory system are responsible for fighting disease?

1. Red blood cells

2. Platelets

3. White blood cells

4. Plasma cells

The correct answer is: White blood cells

White blood cells are crucial components of the immune system and play a key role in fighting disease. Unlike red blood cells, which primarily carry oxygen throughout the body, white blood cells are specifically designed to identify and eliminate pathogens such as bacteria, viruses, and other foreign invaders. There are several types of white blood cells, including lymphocytes (such as B cells and T cells), neutrophils, monocytes, eosinophils, and basophils, each serving unique functions in immune response. For example, B cells produce antibodies that target specific pathogens, while T cells can destroy infected cells or help coordinate the immune response. In contrast, red blood cells are primarily involved in transporting oxygen and carbon dioxide, platelets are essential for blood clotting and wound healing, and plasma refers to the liquid component of blood that carries nutrients, hormones, and waste products but does not directly contribute to fighting diseases. This specialized function of white blood cells makes them the key players in immune defense within the circulatory system.