Common causes of high lymphocyte percentage are: i. Infections, especially gram-negative bacillary infections, such as in the case of typhoid and paratyphoid bacillary infections. ii. Viral infections, such as influenza, viral hepatitis, chickenpox, rubella, cytomegalovirus infections. Third, hematologic diseases: common ones include aplastic anemia. In reblastosis, the proportion of lymphocytes will be significantly higher and the proportion of neutrophils will be significantly lower due to the decrease of hematopoietic tissue and increase of non-hematopoietic tissue in bone marrow. In acute lymphocytic leukemia, a high percentage of lymphocytes and a low percentage of neutrophils can be seen in the peripheral blood due to the proliferation of immature lymphocytes in the bone marrow and their release into the peripheral blood. There is also chronic lymphocytic leukemia, a condition in which near-mature lymphocytes are significantly increased in the peripheral blood and the number of neutrophils is significantly decreased.