**Core Concept:** The Immune response in sepsis is characterized by the total leukocyte count (TLC) and the percentage distribution of different leukocyte types, including neutrophils, lymphocytes, eosinophils, monocytes, and band cells. The Immune response to infection can be assessed by calculating the Immune:Tumor (I:T) ratio.

**Why the Correct Answer is Right:** The I:T ratio is calculated by dividing the percentage of lymphocytes by the percentage of neutrophils. In this case, the lymphocytes percentage is 35% and neutrophils percentage is 40%. The I:T ratio is therefore:

(35/40) = 0.875

**Why Each Wrong Option is Incorrect:**

A. The correct formula to calculate the I:T ratio is (lymphocytes / neutrophils), not lymphocytes / (lymphocytes + neutrophils). This is because lymphocytes and neutrophils are the two main components of the formula.

B. The correct formula to calculate the I:T ratio is (lymphocytes / neutrophils), not lymphocytes / monocytes (which is option D). Monocytes are a different type of white blood cell and should not be included in the formula.

C. The formula to calculate the I:T ratio is (lymphocytes / neutrophils), not lymphocytes / eosinophils. Eosinophils are another type of white blood cell and should not be included in the formula.

D. The correct formula to calculate the I:T ratio is (lymphocytes / neutrophils), not lymphocytes / monocytes. Monocytes are a different type of white blood cell and should not be included in the formula.

**Clinical Pearl:** The I:T ratio is a useful marker to assess the immune response in sepsis patients. A low I:T ratio (0.8) suggests an excessive immune response. A ratio between 0.8 and 1.2 indicates a balanced immune response. This ratio can help guide treatment decisions, particularly regarding the use of corticosteroids, which can suppress the immune system if used excessively.