Although studies evaluating neoadjuvant systemic therapy (NST) have shown that chemotherapy has activity against triple negative breast cancer (TNBC), patients who do not achieve a pathologic complete response (pCR) have poor survival outcomes. This emphasizes the need for novel strategies such as immunotherapy that could be given either to increase pCR rates or in the adjuvant setting to prevent disease recurrence. Hypothesis: We hypothesize that an immune response augments the anti-tumor effect of chemotherapy and that T cell co-inhibitory molecules expressed on TNBC can be targeted therapeutically. Specific Aims: 1) Examine the immune cell infiltrate in TNBC and changes occurring in response to NST, 2) Determine the effect of NST on immune gene signatures, and 3) Evaluate the expression of the T cell coinhibitory molecule PD-L1 in TNBC. Study Design: Studies will be performed using formalin-fixed, paraffin-embedded (FFPE) tissue blocks from pre-and post-NST specimens from 100 TNBC patients. We will perform immunohistochemistry staining for various cell types of adaptive (CD8+ Tcells, CD4+ Tcells, Tregs) and innate (neutrophils, macrophages, and NK cells) immune responses.