Allele-

One of two or more alternative states of a gene.

Amino acids-

The subunit structure from which proteins are produced, consisting of a central carbon atom with a carboxyl group (-COOH), an amino group(-NH2), a hydrogen, and a side group; only the side group differs from one amino acid to another.

Antibody-

A protein called immunoglobin that is produced by lymphocytes in response to a foreign substance (antigen) and released into the bloodstream.  Antibodies are specific for particular antigens.  They enable the body to recognize any future exposure to the antigen and thereby prevent the microbe-carrying antigen from causing disease.

CCR5-

A chemokine receptor found on macrophages.  HIV-1 invades a host cell by binding to the molecules CD4 and CCR5 on the macrophage surface.

CD4-

A protein displayed on the surface of certain immune cells such as macrophages and T-cells.  The CD4 molecules usually participate in signaling between immune cells.   But when HIV enters the picture, CD4 molecules bind to a sugary protein (gp120) protruding from HIV's outer envelope and, in so doing, help the virus gain entry into the cell.

Chemokine-

Short strings of amino acids responsible for luring immune cells to injured or diseased tissues.

Chemokine Receptors-

Seven membrane-spanning molecules bound primarily on the surface of immune cells.   These receptor molecules bind with chemokines, recruiting cells of the immune system to the site of tissue damage or disease.  HIV-1 takes advantage of the presence of these chemokine receptors to gain access to the cell via a fusion-mediated event.  Examples include CCR5 and CXCR4.

Chromosome-

The vehicle by which hereditary information is physically transferred from one generation to the next. In eukaryotes, each chromosome consists of a single linear DNA molecule and associated proteins.

CXCR5-

A chemokine receptor found on the surface of T-cells.  CXCR4 facilitates fusion of HIV and the host cell.  During the T-tropic stage of the virus, HIV-1 binds to CD4 and CXCR4 on the T-cell surface.

Deoxyribonucleic Acid (DNA)-

The genetic material of all organisms; composed of two complimentary chains of nucleotides wound in a double helix.  Local unwinding of the helix by disruption of hydrogen bonds between strands permits RNA polymerase molecules to transcribe mRNA copies of genes, and permits DNA polymerase molecules to replicate copies of the duplex molecule.

Endoplasmic Reticulum (ER)-

An internal membrane system that forms a netlike array of channels and interconnections of organelles within the cytoplasm of eukaryotic cells.  Rough ER synthesizes proteins to be exported, while smooth ER organizes the synthesis of lipids and other biosynthetic activities.

Enzyme-

A protein that is capable of speeding up specific chemical reactions by lowering the required activation energy, but is unaltered itself in the process; a biological catalyst.

Fusion-

The joining of a virus and a host cell; interaction