2-1.Immunity of skin
	●A variety of stimulus qualities such as mold, viruses, and bacilli exist innumerably in our surroundings. When a strong skin is not passed so that these bacilli may enter the inside of the body, it doesn't become it. Epidermis that comes in succession corneum cell in the layer is an organ that is stronger than we think. Moreover, corneum cell peels off and drops like the seat that was settled every day to some degree. The microorganism etc. that started invading peel off together, too and it falls at that time. A new horny layer cell comes in succession from and and the depths of the epidermal gradually.
					●However, stratum important when injuring. Corneum cell might temporarily be ruined damaging corneum. The bacillus invades the inside of the body fast. We will die easily if only stratum corneum is a defense organ of the body. If it is so, our body has the mechanism of various defenses. It is said, 'Immunity'.
	What is immunity?　　　　　　 ●Immunity is 'System that excludes the one other than me from the inside of the body. 'It is working of immunity to exclude non-self distinguishing our body (self) and other one (non-self) and to defend the self. There are greatly two working in immunity , saying that 'Natural immunity' and 'Acquired immunity'. ＜Natural immunity＞ ●Cells such as special enzyme protein or gemastete cells (mast cell) that are called the complement and a lysozyme included in the serum and the body fluid for non-self of the virus, the bacillus that has invaded the inside of the body by being thought non-peculiar immunity, mold, and the helminth, etc. and a multi type nuclear white blood corpuscle, macrophages, and natural killer cells (cell) start excluding these to the natural immunity respectively alone or jointly. ＜Acquired immunity＞ ●Another immunity that is called an acquired immunity works when it is not possible to deal by the natural immunity. In the acquired immunity, the lymphocyte that recognizes only the invasion thing (This is called an antigen) who is non-self who invaded the inside of the body is immune reaction done in the peculiarity by being in the body. The antigen recognized once is permanently memorized by the lymphocyte's that recognized it being in the inside of the body. And, the recognized lymphocyte is activated at once when the attack of the same antigen is received again, and it works when exclude the antigen.