Background: Innate and adaptive immunity affect tumor growth and progression. Likewise, immune cell subsets may have a promising approach in prognosis and treatment strategies. Aim: The aim of this pilot study was to investigate the neoadjuvant paclitaxel's effect on the relative and absolute numbers of lymphocytes, monocytes, granulocytes and CD11b and its maturation markers and their role in breast cancer patients' clinical response. Patients and Methods: Breast cancer patients (n=10) and healthy donors (n=4) were recruited from Tanta Cancer Center, Egypt. Peripheral blood samples (2ml) were collected in EDTA tubes from breast cancer patients during neoadjuvant chemotherapy (prior to each cycle of paclitaxel) as well as healthy volunteers. The relative and absolute numbers of lymphocytes, monocytes and granulocytes were obtained using gating strategy after acquisition with Flow-cytometer. The absolute numbers of CD11b⁺ and its maturation markers (HLADR⁺ and CD83⁺) were also evaluated by flow-cytometry after staining with specific antibodies. The absolute number was calculated using total peripheral blood leucocytes of each subject. Results: Comparing between the absolute number of monocytes prior to each cycle, significant difference was found between the 1^st cycle vs the 3^rd cycle and the 4^th cycle. Significant difference was also found in CD11b expressing cells and its maturation markers (HLADR) between responder and non-responder patients. Conclusion: Our study concluded the importance of CD11b and its maturation marker in clinical response in neoadjuvant BC patients as a prognostic tool. Immunological parameters should be considered during application of treatment strategies as a prognostic tool and promising approach in immunotherapy.