What does HIV do to your cells?

HIV is a retrovirus Genetic information stored as RNA --not DNA. reverse transcriptase copies RNA to DNA inside cell

Steps in HIV replication HIV attaches to and penetrates target cell.

2. HIV releases RNA into cell. RNA copied as DNA

3. Viral DNA enters the cell's nucleus.

4. Viral DNA becomes integrated with the cell's own DNA.

Now host cell will replicate viral RNA 5. DNA of infected cell now produces viral RNA and proteins 6. A new virus is assembled from RNA and short pieces of protein. 7. The virus buds off from the infected cell.

What cells does HIV target? White blood cells called helper T cells Helper T cells activate and coordinate other cells of the immune system that fight disease

How does HIV target the helper T Cells? On their surface, these cells have a receptor called CD4, which enables HIV to attach to them.

What happens once a person is infected with HIV? 40 to 60% of helper T cells are destroyed in the first few months of infection. Fewer helper T cells mean the body is less capable of fighting off disease—including the HIV that is already present.

When HIV becomes AIDS If the CD4 count falls below about 200 cells per microliter of blood The presence of opportunistic infections

Drug resistance HIV mutates easily during the conversion of viral RNA to DNA because reverse transcriptase is prone to errors.

What is the body’s immune system? Response to any and all pathogens that enter (or try to enter) (path- = disease, gen = generate or cause)

First line of defense (nonspecific) Barriers --skin: barrier pathogen can’t cross --sweat, saliva, tears: wash pathogen away or use enzymes to break it down --mucous membranes: trap and expel pathogen

Second line of defense (nonspecific but internal) White blood cells --macrophages (big eaters) they eat strangers

White blood cells (con’t) --neutrophils also eat strangers but die themselves in doing so --natural killer (NK) cells kill strangers by puncturing their membranes

Inflammatory response Mast cells release histamines --alarm: pathogen has invaded! Phagocytes come in to eat them

Certain proteins Interferon --interferes with virus reproduction --original infected cell dies, but others protected

3rd line of defense— targeted to specific invaders White blood cells called lymphocytes B cells (develop in Bone marrow) Have antibodies T cells (develop in Thymus) Activators, killers of pathogens that have locked with antibodies

How do B cells and T cells recognize their targets? Invading pathogens have antigens—(molecules on their surface that generate an immune response) B cells have antibodies on their surfaces. Each cell recognizes (has antibodies for) one specific antigen.

Helper T cells—the key to it all B cells and cytotoxic T cells must be activated in order to do their job Helper T cells activate the B cells and cytotoxic T cells that are needed for a specific pathogen

Immunity Passive— birth to about 3 months, comes from mom’s antibodies

Immunity Natural If you’ve had a certain disease (say chicken pox), your body already has antibodies for it and a “memory” of the disease to create more. So you can’t get the disease again.

Immunity Vaccination --A killed virus or virus look-alike is injected --Its antigens cause your body to develop antibodies --Those antibodies will be ready for action if the real virus invades