Chapter 1, Problem 1Q

Summary Introduction

(a)

To write:

The name of the primary lymphoid tissues in mammals and the main types of secondary lymphoid tissue.

Introduction:

Lymphoid tissues can be defined as organized structures that are a vital part of the immune system. It protects the body from infections and potential pathogens. Some of the important lymphoid tissues are spleen, bone marrow and thymus.

Explanation of Solution

The lymphoid tissues are divided into two types according to their functions. They are primary and secondary lymphoid tissues. Primary lymphoid tissues include bone marrow and thymus. Apart from them, every other type of lymphoid tissue is known as secondary lymphoid tissue. The main secondary lymphoid tissues include the spleen, mucosa-associated lymphoid tissues (MALT) and lymph nodes. These also include gut-associated lymphoid tissue (GALT), such as the adenoids, tonsils, Peyer's patches, appendix and bronchial-associated lymphoid tissues (BALT).

Conclusion

Therefore, primary lymphoid tissues are bone marrow and thymus and the main secondary lymphoid tissues include the spleen, mucosa-associated lymphoid tissues (MALT) and lymph nodes.

Summary Introduction

(b)

To write:

The differences in functions of primary and secondary lymphoid tissues and discuss the principal events that take place in each.

Introduction:

Lymphoid tissues can be defined as organized structures that are a vital part of the immune system. It protects the body from infections and potential pathogens. Some of the important lymphoid tissues are spleen, bone marrow and thymus.

Explanation of Solution

Central or primary lymphoid tissues are the anatomical locations where lymphocytes get developed and reach the state of maturation required where they can respond to a potential pathogen. B cells are matured in the bone marrow and fetal liver before entering the circulation, whereas T cells mature leave the bone marrow at the immature stage and mature in the thymus. Both lymphocyte lineages are derived from a common hematopoietic stem cell.

Secondary lymphoid tissues are the anatomical locations where lymphocytes encounter antigen and immune responses get induced. Antigen is delivered to the secondary lymphoid tissues through an afferent lymphatic vessel. It is reserved in the lymphoid tissue to encounter with lymphocytes having antigen specific receptors.

Conclusion

Therefore, primary lymphoid tissues are the anatomical locations where lymphocytes get developed and reach the state of maturation required where they can respond to a potential pathogen. Whereas, secondary lymphoid tissues are the anatomical locations where lymphocytes encounter antigen and immune responses get induced.