Immune System Organs

The immune system plays an important role in maintaining a healthy body free of diseases. This is the main reason why, some people with a compromised immune system are more susceptible to health conditions, while others are resistant against the same diseases. To be more precise, it is this defense mechanism that decides the fate of tumor cells, bacteria, viruses, parasites or other pathogens, whether they will succeed in invading the body or not.

Similar to other organ systems of the body, the immune system comprises a group of cells, tissues and organs that collectively help in protecting the host from intruding foreign particles and pathogens. Let's take an example; when a disease causing microbe attacks the body, the organs identify it first and produce a suitable antibody to destroy the microbe. This way, immune system functions in response to unwanted pathogens. Let's take a look at the network of human immune system organs.

Cells of Immune System

The cells that make up the immune system are white blood cells (WBCs), also known as leukocytes. Based on the responses, there are two types of immune system - innate and acquired. The former category protects the body from infections in a generalized or non-specific manner. Cells of the innate immune system are basophils, eosinophils, natural killer cells, mast cells and phagocytes (dendritic cell, macrophages and neutrophils). In contrary to the innate type, the acquired or adaptive immune system provides specific, long-term protection to the host. Cells that make up acquired type are lymphocytes (B and T lymphocytes).

Organs of Immune System

The leukocytes are produced and stored in certain tissues and organs of the body. The organs that actively participate in generation of lymphocytes are called primary lymphoid organs, while others that act as site for immune responses are called secondary lymphoid organs. Besides these, tertiary lymphoid organs aid in importing lymphocytes whenever necessary. Discussed below are the main organs of the immune system:

Thymus: Thymus is present at birth and continues to grow until the onset of puberty. It a primary lymphoid organ, located in between heart and the breastplate. Resembling a butterfly in shape, thymus has the major function of directing the maturation of thymocytes to T lymphocytes. The T cells are crucial for identifying self cells and foreign particles.

Bone Marrow: Bone marrow, present inside the bones, is not actually an organ, but it is essential for the functioning of immune system. Hence, it is often considered as a primary lymphoid site. Over here, immature thymocytes, B cells and other lymphatic cells are originated. Some of these cells mature in the bone marrow itself, while others are circulated to different parts to undergo maturation.

Lymph Nodes: Lymph nodes are bean shaped structures that house lymphocytes, dendritic cells and macrophages. They help in filtering lymph, which are nothing but the fluids circulated after draining from the body tissues. During this process, unwanted particles are destroyed. The fluids after filtration in the lymph nodes are released back to the bloodstream.

Spleen: Situated in the left side of the abdominal cavity, spleen is a secondary lymphoid organ that contains many T cells. These cells detect the presence of foreign particles, when blood circulates takes place over this organ. Spleen performs several functions, ranging from filtering the blood to destroying the unused blood cells.

Mucosal Associated Lymphoid Tissues (MALT): The mucus lining of the respiratory, digestive and urogenital tracts are prone to microbial entry. MALT is a secondary lymphoid organ, containing plasma cells that produce antibodies. Its main function is to defend the microbes making their way through the mucous lining.

Cutaneous Associated Lymphoid Tissues (CALT): Another tertiary lymphoid organ is the skin. It is a basic part of immune system, which acts as a barrier to prevent foreign particles from entering inside the host. The large surface area of the skin is effective in providing nonspecific defenses (innate) to the host body.

Speaking about immune system diseases, any abnormality of the immune responses, either underactive or overactive can lead to various illnesses. In a nutshell, proper interaction of immune system organs, lymphatic system and circulatory system are crucial to respond effectively against foreign bodies and infections.