Final answer:
Lewise antigens are on type II precursor chains but not well developed at birth, and while antibodies to them can cause HTRs, they do not always do so and rarely cross the placenta. Anti-Rh antibodies, in contrast, are produced upon sensitization and can cross the placenta, leading to HDN in subsequent Rh+ pregnancies.option(a).
Step-by-step explanation:
The Lewis antigen system relates to the blood group antigens found on red blood cells (RBCs). The question primarily concerns the characteristics of Lewis antigens and the associated immune responses. To address the points raised in the question:
- Lewis antigens are indeed found on type II precursor chains of carbohydrates played out on the surface of RBCs.
- Lewis antigens are not fully developed at birth, they mature during early childhood, which makes this statement false.
- While antibodies to Lewis antigens can cause hemolytic transfusion reactions (HTRs), they do not always do so, particularly because they tend to be naturally occurring and may not always be clinically significant in transfusion settings.
- Antibodies to Lewis antigens indeed rarely cross the placenta. This is attributed to the fact that they are usually IgM antibodies, which are too large to cross the placental barrier.
As for the Rh antigen system, Rh factor antigens trigger a primary antibody response upon exposure to Rh positive (Rh+) RBCs in individuals with Rh negative (Rh-) blood. A previous sensitization event is required to generate anti-Rh antibodies, which are typically IgG and can cross the placenta. This becomes clinically significant in subsequent pregnancies where a Rh- mother may carry an Rh+ fetus, leading to the risk of hemolytic disease of the newborn (HDN).