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What Exactly is HIV/AIDS and How Does it Infect the Body

Updated on August 7, 2017

The Human Immune System

The human body has a well organized and complex immune system which protects us from disease causing bugs, toxins, cancers and most compounds foreign to the body. The cells that make up the immune system are known as white blood cells or leukocytes. There are many types of white blood cells, all with specific functions:

Type of White Blood Cell
% by Volume of White Blood Cells
Function
Neutrophills
60-70
First line of defense against invading microorganism
Eosiniphils
2-4
Invoilved in allergic reactions
Basophils
<1
Inflammatory reactions, especially allergy causing
Lymphocytes (B-cells and T-cells)
20-25
Release of antibodies and signalling other cells of the immune system
Monocytes (Macrophage and dendritic cells)
4-8
Phagocytosis("eating" away) and relase of signalling chemicals(cytokines)
Cell infected with HIV
Cell infected with HIV | Source

What is HIV

HIV stands for Human Immunodeficiency virus. Like most viruses, it is very specific in that it can only infect humans, usually the white blood cells.

The virus commonly attacks specific types of white blood cells called dendritic and helper T-helper cells. The HIV does this by attaching to, penetrating and hijacking cellular mechanism of the white blood cells to multiply in number, hence sabotaging the function of the infected cells. However, attaching to and getting inside the cell it is not a simple feat: one, the cells have a physical barrier that keeps out bugs, and two, other immune cells and internal cell defenses relentlessly attempt to destroy the virus. The HIV has several methods of overcoming these challenges.

How HIV gets into the body:

The HIV is transmitted from an infected person only through specific body fluids: blood, semen, pre-seminal fluids, rectal fluids and breast milk.

Can you get AIDS from saliva?

Contrary to most beliefs HIV is not spread through saliva. The properties of saliva disrupt cells containing the virus and inhibit their potential to infect other cells. HIV is transmitted through behaviors in which the named fluids are exchange such as:

i)Sexual intercourse- vaginal or anal sex

iii)Sharing syringes and needles i.e in drug users

iii) Transfusion with infected blood (rare as blood is usually screened)

iv) Breastfeeding

v) Mother to child- during childbirth


Once in the Body

Once inside the body the immune immune systems starts to produce anti-HIV antibodies and Cytotoxic T cells. Antibodies act like tags which stick onto the virus marking it , thus making it easy for other immune cells to identify and destroy the virus. Cytotoxic T-cells inject toxic chemicals into infected cells, consequently destroying the virus. However it can take the body months to produce enough antibodies to combat the virus.

How does HIV attach to and penetrate the cells?

All Cells have small protrusions i.e. receptors that stick out from its their surfaces. Cells communicate to each other through these receptors. Different signals cause changes on receptors which in turn creates a cascade of reactions bringing change within the cell. To attach to the cell, HIV binds to the immune cells through receptors called CD4+. CD4+ receptors are mostly found in T-helper cells. Receptors act like lock and key, and HIV receptors have evolved to be a perfect match for CD4+ receptors. This is the reason why HIV affects only humans. The interaction of the HIV and cell receptors causes the cell to open up, allowing entry of the virus. Once in the cell, the genetic material of the virus is released into the cell. The virus has special enzymes and machinery that cut into the human DNA code and inserting their own. Since cells are continuously multiplying and replicating their DNA, they inevitably do the same for the virus. An infected cell will blindly use the viral DNA code to create new viruses. At this time the HIV has infiltrated and hijacked the cell.

HIV carrying Dendritic cell interacting with a T helper cell
HIV carrying Dendritic cell interacting with a T helper cell | Source

Effect on Immune system/AIDS

Dendritc and T- helper cells act like alarms for the body. Once a dendritic comes in contact with HIV, it attaches to it, and transports for processing by T cells in the lymph nodes, where they are produced. In the case of other bugs, the The T-helper cells would then multiply rapidly, and in their mature form T helper cause the creation of necessary antibodies and the activation other immune cells. However, once HIV has attached to dendritic cells, its interferes with the ability of dendritic cells to communicate effectively with the T-helper cells. Infected cells are a targeted for destruction by other cells of the immune system. Infected T- helper cells in production also detect the presence of HIV DNA in their genome and go through a form of cell suicide to protect the host.

Overtime, the continuous cell death results in reduced numbers of dendritic and T-helpers. Once T- helper cells (CD4+) fall below 200 cells per micro-Liter of blood sample, it is referred to as AIDS(Acquired Immunodeficiency Syndrome). The body is no longer able to effectively recognize and fight threats becomes susceptible to otherwise harmless bugs. Even a simple Influenza virus can prove dangerous for person with AIDS. Development AIDS is the last stage of HIV infection.


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