The lymphatic system is involved with the immune and circulatory systems. It's responsible for removing toxins and waste from the blood and fighting illnesses. A way that it works with the circulatory system is by transporting a fluid called lymph, which fights infections, through the capillaries, veins and arteries of the body. If you've heard of "lymph nodes", then you already know one part of the system. These organs are responsible for processing the lymph, and you have quite a few of them.
One organ that is major in the system is the spleen. It's a kinda bean shaped organ located right under your left rib cage above the stomach. I think it's one of those less-known organs, as well. Its job is to make sure your body has the right amount of blood in it, filter red blood cells, and fight infection. That's why if you don't have a spleen, you're more prone to getting sick and I've heard that you'd have to get more vaccines for things that your body normally can fight off on its own. So it's a vital part of the immune system. It processing old red blood cells out and regulating how much blood you have links it to the circulatory system. If your body has old RBCs that are defective or not working anymore, your spleen gets rid of them.
Hope this helps.