Immunoblasts

Immunoblasts can be of B-cell or T-cell origin and reside in the perifollicular zones of secondary lymphoid tissue (such as lymph node) where they are morphologically indistinguishable. They are large cells with abundant cytoplasm, large nucleus with open chromatin, and a single centralized large nucleolus. They are part of the developmental stage of lymphocytes which follow the presentation of an antigen by MHC class II positive antigen presenting cells.