What is a Virus? What are Viruses made up of ?

3. Immune Responses to Virus.

Figure 2 Diagram of influenza viral replication in the host cell, and how immune responses work against this (ie antibody production and T cell response). Viruses attempt to enter the cell ( top left), through interactions between molecules on their surface and those of the host cell. Upon entry, their genetic material replicates within the cell nucleus (middle), and manufactures viral proteins that are repackaged into virus, and released via budding (top right). Antibodies (Y-shaped, various colours) can interfere with interaction of the cell surface receptors, blocking entry into the cell; or can stop proteins being correctly packaged and made into new infectious virus particles. Other antibodies can enable immune components such as natural killer cells and complement systems to recognise virus-infected cells and trigger their death.
T-cells (bottom right) can further recognise specific viral antigens expressed on the surface of the host cell, and destroy it, preventing any further viral replication. Vaccines are designed to elicit these same antibody and T cell responses". 
Click on image to enlarge