الصف :الحادي عشر - العام الدراسي :2014/2015
The immune system is a network of cells, tissues, and organs that work together to defend the body against attacks by ``foreign`` invaders. These are primarily microbes (germs) – tiny, infection-causing organisms such as bacteria, viruses, parasites, and fungi .Because the human body provides an ideal environment for many microbes, they try to break in. It is the immune system`s job to keep them out or, failing that, to seek out and destroy them
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حلقة بحث97THE IMMUNE SYSTEM
