Lethally irradiated mice were split into 4 groups, and experiments were conducted as described below:

Group 1 was not given any cells.

Group 2 was given thymus-derived cells from a syngeneic donor, and two months later, immunized with a polysaccharide antigen

Group 3 was given bone marrow cells from a syngeneic donor, and two months later, immunized with a polysaccharide antigen.

Group 4 was given bone marrow cells from a syngeneic donor, and two months later, immunized with a T-dependent antigen.

Four possible outcomes, listed below, were suggested:

A. Group 1 mice are unlikely to survive.
B. Group 2 mice are likely to produce antibodies in response to polysaccharide antigens.
C. Group 3 mice are likely to produce antibodies in response to polysaccharide antigens.
D. Group 4 mice are likely to produce antibodies in response to T-dependent antigens.

Which one of the following options represents the combination of all correct statements?

Correct option is D

Explanation of Each Statement:

Statement A: Group 1 mice are unlikely to survive.
Lethally irradiated mice cannot regenerate immune or hematopoietic cells on their own.
Without any cell transplant, they lack bone marrow and thymus-derived cells essential for survival.
Hence, Group 1 mice will die due to immune deficiency. 

Correct

Statement B: Group 2 mice are likely to produce antibodies to polysaccharide antigens.
Group 2 received only thymus-derived cells.
Polysaccharide antigens are T-independent antigens — they primarily stimulate B cells, not T cells.
Since bone marrow (B-cell source) was not provided, the mice cannot produce antibodies to polysaccharide antigens.
 Incorrect

Statement C: Group 3 mice are likely to produce antibodies to polysaccharide antigens.
Group 3 received bone marrow cells, which can give rise to B cells.
Polysaccharide antigens are T-independent, so T cells are not required for this antibody response.
These mice should be able to produce IgM antibodies against polysaccharide antigens.
 Correct

Statement D: Group 4 mice are likely to produce antibodies in response to T-dependent antigens.

Group 4 received bone marrow cells, which give rise to B cells, and sufficient time (2 months) for immune reconstitution.
T-dependent antigens (like proteins) require T-cell help, and the thymus-derived T cells from the bone marrow precursors will be functional by this time.
Hence, Group 4 can respond to T-dependent antigens.
 Correct