Question

question 46

although there are rare exceptions, which of the following best describe most examples of lewis antibodies?

• igg, in vitro hemolysis, do not cause htr
• igg, in vitro hemolysis, cause htr
• igm, naturally occurring, do not cause hdfn.
• igm, naturally occurring, cause hdfn

Explanation:

Identify antibody class and origin

Using the Lewis Blood Group knowledge point

• Lewis antibodies (anti-\(\text{Le}^\text{a}\) and anti-\(\text{Le}^\text{b}\)) are almost exclusively naturally occurring IgM antibodies.
• They are produced without exposure to foreign red blood cells through transfusion or pregnancy.

Assess clinical significance in HDFN

Using the Lewis Blood Group knowledge point

• IgM antibodies are large pentamers and cannot cross the placenta.
• Lewis antigens are poorly developed on fetal and newborn red blood cells.
• Consequently, Lewis antibodies do not cause Hemolytic Disease of the Fetus and Newborn (HDFN).

Evaluate the given options

Using the Lewis Blood Group knowledge point

• "IgG, in vitro hemolysis, do not cause HTR": Incorrect, they are primarily IgM.
• "IgG, in vitro hemolysis, cause HTR": Incorrect, they are primarily IgM.
• "IgM, naturally occurring, do not cause HDFN": Correct, matches the biological characteristics.
• "IgM, naturally occurring, cause HDFN": Incorrect, they do not cross the placenta or bind well to newborn cells.

Answer:

• (A) IgG, in vitro hemolysis, do not cause HTR
• (B) IgG, in vitro hemolysis, cause HTR
• (C) IgM, naturally occurring, do not cause HDFN. (Correct answer)
• (D) IgM, naturally occurring, cause HDFN