These systems are important in fighting off infection. the endocrine system and the immune system the immune system and the cardiovascular system the integumentary system and the respiratory system the immune system and the lymphatic system

The immune system and the lymphatic system

Explanation:

The lymphatic system is apart of the immune system and is very important because it basically helps the general functioning of the immune system and without it the immune system wouldn't work.

The lymphatic system and the immune system

Explanation:

The endocrine system consists of glands that produce hormones to control your body's activities. These can include the pituitary, adrenal, ovaries, testes, etc., which do not relate battling off an infection. The cardiovascular system is an equally important system that is dedicated to circulating your blood through various types of blood vessels and transporting gases, hormones, etc., which does not help at all with battling off an infection, and in fact can allow it to spread and worsen. The integumentary system, consisting of skin, hair, and nails, is meant to serve as a defense layer and provide protection, but not to stop an infection, which leaves us with the last answer, the immune system and the lymphatic system that we can, therefore, determine as the correct answer. For further proof, the lymphatic and immune system do actually work together to battle pathogens, viruses, and infections, which is what the question is asking about.

Hope this helped! :]