1 Introduction

The hemolymphatic system is composed of the hematopoietic system, cells within the circulation, and the lymphoid system. The hematopoietic system is largely restricted to the bone marrow, while the cells of the circulation are found not only in the blood, but often migrate into tissues. The lymphoid system is widely distributed and is part of several organs, including the lymph nodes, spleen, and various distributed “associated lymphoid tissues” (ALTs), such as the mucosal associated lymphoid tissue (MALT), bronchiolar associated lymphoid tissues (BALT), etc. Regardless of the location of the lymphoid tissue, it’s normal immunological reaction is the same.

The separation of topics in this section is a bit artificial, and could easily be organized differently. The presentation here is the way in which it makes most sense to me, but you may find the organization in the reference textbook more to your liking. The information is the same.