The effects of ischemic stroke on the systemic circulation include: a. increased susceptibility to infection b. sensitization of circulating lymphocytes to brain antigens c. both \(a\) and \(b\) d. neither a or b

First, we need to understand what an ischemic stroke is and what effects it might have on the systemic circulation. An ischemic stroke occurs when the blood supply to a part of the brain is interrupted or reduced, causing brain tissue to be deprived of oxygen and nutrients. As a result, the brain cells start to die within minutes.

Now, let's analyze each of the choices: a. Increased susceptibility to infection: It is known that patients who have suffered an ischemic stroke have a higher risk of developing infections due to the altered immune response and the damage to the blood-brain barrier. Thus, this option seems to be a correct effect of ischemic stroke on the systemic circulation. b. Sensitization of circulating lymphocytes to brain antigens: As a consequence of the blood-brain barrier damage and immune system dysfunction following an ischemic stroke, lymphocytes can get sensitized to brain antigens, which can lead to an autoimmune reaction targeting the affected brain tissue. This option is also a correct effect of ischemic stroke on systemic circulation.

Now that we have determined that both options a and b are correct, let's compare them to the other given choices: c. Both a and b: Since we confirmed that both options a and b are correct, this choice is the right answer. d. Neither a or b: We have already established that both a and b are correct, so this choice is incorrect.

Based on our analysis, the correct answer is option "c. both a and b", as both increased susceptibility to infection and sensitization of circulating lymphocytes to brain antigens are effects of ischemic stroke on the systemic circulation.