Solution:

• Spleen is the largest organ of the immune system.
• About 4 inch of size, purple in colour, about 200 gms weight.
• Located above the abdomen on the left side of the stomach.
• It contains 2 types of tissues. Red pulp tissues filter and remove old and damaged RBCs present in blood. The resuable components in it, like iron are protected.
• White pulp cells store T cells and B cells which are the main components of the immune system.
• Spleen is considered as the armoury or military camp of the body.