Teacher resources and professional development across the curriculum

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Unit Chapters
Genomics
Proteins & Proteomics
Evolution & Phylogenetics
Microbial Diversity
Emerging Infectious Diseases
HIV & AIDS
Introduction
The Immune System
The Central Role of Helper T Cells
The Structure and Life Cycle of HIV
Progression of HIV Infection
Treatments Based on Understanding the Viral Life Cycle
The Challenges of Vaccine Development
Social Obstacles to Controlling HIV
Genetics of Development
Cell Biology & Cancer
Human Evolution
Neurobiology
Biology of Sex & Gender
Biodiversity
Genetically Modified Organisms
The Immune System

Understanding the various components of the immune system and the complex signaling that takes place between immune cells is key to understanding HIV. Both non-specific and specific lines of defense help thwart the invasion of pathogens. Non-specific defenses act quickly and indiscriminately to exclude microbes from the body or actively kill intruders. Mechanical barriers - such as the mucus, hairs, and cilia in the respiratory tract, and the flow of urine through the urinary tract - are among these non-specific defenses. Skin oils and chemicals in perspiration and gastric juices also serve as non-specific barriers. Mechanisms involving complex chemical signals such as fever and inflammation also act against a wide variety of pathogens. One non-specific defense involves phagocytes, a particular type of leukocyte (white blood cell), which act as cellular "Pac-Men," engulfing and digesting microbes or other irritants like dust and pollen.

Table 1: Types of Leukocytes
If invaders have breached the non-specific defenses, the immune system will use a variety of leukocytes to mount directed defenses against specific invaders. Lymphocytes bind and respond to specific foreign molecules (antigens). One subset of lymphocytes, the B cells, matures into antibody-secreting cells. Another subset of lymphocytes, the T cells, includes immune cells that directly kill cancerous or virally infected cells. Some subtypes of T cells serve a regulatory function, releasing chemical signals that can stimulate or suppress a variety of immune functions. Because HIV preferentially infects one of these regulatory T cells, the so-called helper T (TH) cell, it can subvert and decimate the immune system, leading to AIDS.

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