The nurse cares for the client with a history of pulmonary tuberculosis (TB). Two granulomas were present in the chest x-ray. Which explanation does the nurse understand best describes the primary immune response to tuberculosis infection?

Choice A reason: Weight gain is not a common complication of Crohn's disease because Crohn's disease causes inflammation and ulceration of the digestive tract, which can lead to malabsorption, diarrhea, and weight loss.

Choice B reason: Perianal fistula is a common complication of Crohn's disease because Crohn's disease can cause deep ulcers that penetrate the bowel wall and create abnormal connections between the bowel and the skin around the anus. Perianal fistulas can cause pain, bleeding, infection, and fecal incontinence.

Choice C reason: Vomiting after meals is not a common complication of Crohn's disease because Crohn's disease mainly affects the small intestine and the colon, not the stomach. Vomiting after meals can be a sign of gastric ulcers, gastritis, or gastroparesis.

Choice D reason: Urinary tract infections are not a common complication of Crohn's disease because Crohn's disease does not directly affect the urinary system. However, some people with Crohn's disease may develop enterovesical fistulas, which are abnormal connections between the bowel and the bladder. Enterovesical fistulas can cause urinary tract infections, hematuria, and pneumaturia.

Choice A reason: Decreased dietary intake of proteins and vegetables is not the best explanation because it is a factor that affects the nutritional status, not the immune system. Nutritional status is important for maintaining the health and function of the body, but it does not directly cause an increased risk of infection. Proteins and vegetables are sources of essential nutrients, such as amino acids, vitamins, minerals, and antioxidants, that support the growth and repair of the tissues and the prevention of oxidative stress.

Choice B reason: Decreased T cell function and antibody response is the best explanation because it is a factor that affects the immune system, which is the body's defense mechanism against foreign invaders, such as bacteria, viruses, and fungi. The immune system consists of two main components: the innate immunity and the adaptive immunity. The innate immunity is the first line of defense that provides a general and rapid response to any potential threat. The adaptive immunity is the second line of defense that provides a specific and long-lasting response to a particular antigen. T cells and antibodies are part of the adaptive immunity, which recognizes and remembers the antigens that have previously infected the body and eliminates them more efficiently. However, as people age, the T cell function and the antibody response decline, making the older adults more susceptible to infections, especially those that are new or unfamiliar to the body.

Choice C reason: Atrophy of the bone marrow and spleen is not the best explanation because it is a factor that affects the production and storage of immune cells, not the function and response. The bone marrow is the soft tissue inside the bones that produces the blood cells, including the white blood cells, which are the main components of the immune system. The spleen is an organ that filters the blood and removes the old or damaged blood cells, as well as stores some of the white blood cells and platelets. As people age, the bone marrow and the spleen shrink and lose some of their ability to produce and store the immune cells, which can reduce the number and diversity of the immune cells available to fight infections. However, this does not necessarily affect the function and response of the immune cells that are already circulating in the blood.

Choice D reason: Impaired absorption of vitamin B12 is not the best explanation because it is a factor that affects the nervous system and the blood cells, not the immune system. Vitamin B12 is a water-soluble vitamin that is essential for the synthesis of DNA, the maintenance of the myelin sheath, and the formation of red blood cells. As people age, the absorption of vitamin B12 decreases due to the reduced secretion of stomach acid and intrinsic factor, which are needed to break down and bind to the vitamin B12 in the food. This can lead to vitamin B12 deficiency, which can cause symptoms such as fatigue, weakness, numbness, tingling, memory loss, and anemia. Anemia is a condition where the blood has a low level of hemoglobin, which is the protein that carries oxygen in the red blood cells. Anemia can affect the oxygen delivery to the tissues, but it does not directly cause an increased risk of infection.