Question

Case study

When a microorganism invades a host, a definite sequence of events usually occurs leading to infection and disease, causing suffering to the host. This process is called pathogenesis. Once a microorganism overcomes the defense system of the host, development of the disease follows a certain sequence of events as shown in the graph. Study the graph given below for the sequence of events leading to appearance of a disease and answer the questions that follow :

(a) In which period, according to the graph there are maximum chances of a person transmitting a disease/infection and why?

(b) Study the graph and write what is an incubation period. Name a sexually transmitted disease that can be easily transmitted during this period. Name the specific type of lymphocytes that are attacked by the pathogen of this disease.

OR

(b) Draw a schematic labelled diagram of an antibody.

(c) In which period, the number of immune cells forming antibodies will be the highest in a person suffering from pneumonia?

Name the immune cells that produce antibodies

Answer 1

(a) According to the given graph, during the period of mild signs or symptoms, there is maximum chance of a person transmitting disease.

It is because, during this period the number of microorganisms are more as they continue replicating themselves due to low titre of antibodies.

(b) The time period between infection and appearance of symptoms of a disease is called incubation period.

HIV can be easily transmitted during incubation period. HIV, the pathogen of AIDS, attacks helper T-lymphocytes.

OR

(b)

(c) Period of decline.

- Antibodies are produced by B-lymphocytes.