Examine the figure below.

Which events have occurred previously to create the situation depicted with the bacterium shown in this figure?
A) The bacterium has successfully overcome the first two barriers of the host's immune response: its barriers and the adaptive response.
B) The presence of an antibody molecule indicates that the antigen has been contacted by a B cell,the B cell underwent cloning,and one of the cloned effector cells has begun antibody production.
C) A cytotoxic T cell recognized the bacterium's antigen and transferred the toxic complement protein directly onto its surface.
D) The bacterium has phagocytized a lymphocyte and is using the captured complement protein to mask itself from other immune cells.

Question

Examine the figure below.

Which events have occurred previously to create the situation depicted with the bacterium shown in this figure?
A) The bacterium has successfully overcome the first two barriers of the host's immune response: its barriers and the adaptive response. 
B) The presence of an antibody molecule indicates that the antigen has been contacted by a B cell,the B cell underwent cloning,and one of the cloned effector cells has begun antibody production. 
C) A cytotoxic T cell recognized the bacterium's antigen and transferred the toxic complement protein directly onto its surface. 
D) The bacterium has phagocytized a lymphocyte and is using the captured complement protein to mask itself from other immune cells.

Quizplus · Accepted Answer

The presence of an antibody molecule indicates that the bacterium has been encountered by a B cell, undergone cloning, and one of the resulting effector cells has started to produce antibodies. This suggests that the host's adaptive immune response has been triggered, which would require the bacterium to have bypassed the first line of defense (barriers such as skin and mucus) and passed the innate immune response. Choice A suggests that the bacterium has bypassed both the innate and adaptive immune responses, which is unlikely as the adaptive response is a highly specific and effective response. Choice C suggests a response by a cytotoxic T cell, which would only occur if the bacterium has infected a cell within the host already. Choice D does not make sense as complement proteins are not used to mask oneself from the immune system.

Examine the Figure Below