There are four main organs that are involved with the lymphatic system.
They are the spleen, thymus, tonsils and adenoids.

The Spleen
This organ is found in the upper left abdominal cavity and is the largest
lymphatic organ in the body. The spleen consists of two types of tissue
called the white and red pulp. The white pulp consists mainly of
lymphocytes and the red pulp consists of venous sinuses which are filled
with blood and cords of lymphatic cells.

The function of the spleen is to filter blood, similar to the way lymph
nodes filter lymph, but it also breaks down and destroys old red blood
cells, which have a life span of around 120 days. The spleen holds extra
blood that can be released into the circulatory system if needed.

The Thymus
As already discovered, the thymus is an endocrine gland but it also
helps to produce white blood cells, so that puts it in the lymphatic
system as well.

The Tonsils
The tonsils are two glands in the back of your throat, and they help to
protect the entrance of the digestive system by preventing bacteria
from entering. When the tonsils become infected, a condition called
tonsillitis occurs. The lymphoid tissues in the back of the mouth at the
top of the throat that normally help to filter out bacteria.

The Adenoids
The adenoids are lumps of tissue found at the back of the nose above
the tonsils but are only present in children as they begin to shrink by the
age of 7. The appendix also needs to be mentioned as, although its
function is unclear, it has a rich supply of lymph tissue.