Obtain pictures of the leukocytes of the immune system as well as various colors of clay that match the colors of those cells. Talk to the class about the different immune system leukocytes, such as by holding up a picture, stating the name of that particular kind of cell and the function of that cell. Place the pictures where everyone can see, pass out the clay and tell them to pick a cell to make a model.
Obtain cotton swabs and one petri dish with agar agar on the bottom for every student. Have each student open the dish, swab the inside of their cheek with the cotton swab, rub the cotton swab on the agar agar without pushing into the agar agar, and put the lid back on the dish. Have the students check their dishes every day. Bacteria should grow in the dishes. Integrate this with talking about why it is important to keep clean, and how the body must protect against various types of bacteria.
Draw an outline of a human on a piece of paper, and in this outline draw outlines of the various immune system organs. Label these organs. Make a copy of this picture for each student, plus extras. Designate a color for each organ of the immune system and color the organs accordingly on the original to have a key of what color goes with which organ. Pass out the student copies, along with colored pencils, crayons or markers. Let them draw a face on their piece of paper. Talk about each organ's function, and after talking about each organ, tell the students to color the organ with the color you have chosen.
Have the students make up a trivia game on the immune system. Draw a basic game board with a path of squares. Discuss what to put in the sections of the path, such as what symbol to have on a square where a player must answer a question. Have the students submit questions with answers, and fact check them. Then assign students to write the approved questions on squares of cardstock, have all the students decorate the cardstock and place them in a box. Tell the students to make a personal game pawn, and to color several things on the board.