I saw the word plasma cell and it immediately got my attention!
Plasma cells are notoriously difficult to target and treat, thus why treatments for multiple myeloma (plasma cell myeloma) are often times not successful. They are hardy little buggers, to put it bluntly. To toss in a little bit more confusion on the issue, the transition from mature B cell to plasma cell is not necessarily a discrete, quantum leap. There are numerous intermediaries along the way, some with more surface Fc receptors, less cytoplasmic Ig, and others more akin to mature plasma cells with few surface Fc and abundant Ig in cytoplasm. We see proof of this in the great diversity of mature B cell lymphoma subtypes. Sometimes, it can be very difficult to fit some of these cells into a definite diagnostic category. Also, some seemingly mature plasma cells show surface expression of CD20, so may in fact get targeted and depleted by Rituxan. One of the statements in the article I don't agree with is that splenic plasma cells lack CD138 expression. To my knowledge, that antigen is a defining feature of plasma cell differentiation. I have seen plenty of CD138 positive plasma cells in splenic tissue! Perhaps they are referring to splenic marginal zone, or post germinal center, B cells. Anyhow, interesting post!