Influenza is an infectious disease caused by a virus. It is possible to have influenza more than once. Which statements explain why it is possible to have influenza more than once? 1 The viral antigens change as a result of mutations. 2 The immune system may be weak and make few B-memory cells. 3 Untreated HIV infection has resulted in a low T-helper cell count.

1, 2 and 3

1 and 2 only

1 and 3 only

2 and 3 only

Biology

IGCSE&ALevel

CAIE

Exam No：9700_s24_qp_13 Year：2024 Question No：40

Answer:

11.2.1 relate the molecular structure of antibodies to their functions

11.2.2 outline the hybridoma method for the production of monoclonal antibodies

11.2.3 outline the principles of using monoclonal antibodies in the diagnosis of disease and in the treatment of disease

11.2.4 describe the differences between active immunity and passive immunity and between natural immunity and artificial immunity

11.2.5 explain that vaccines contain antigens that stimulate immune responses to provide long-term immunity

11.2.6 explain how vaccination programmes can help to control the spread of infectious diseases