b. Red blood cells from newborn infants give unreliable reactions with anti-Lea
and are usually negative with anti-Leb. In subjects destined to be Le(a-b+), the red
blood cells go through an intermediate Le(a+b+) phase during the first few years of life.
c. Two other antigenic determinants, Lec and Led, have been described. The
rare antibodies detecting these determinants react with Le(a-b-), but not Le(a+) or
Le(b+) red cells. The biochemical structure of these antigens has not yet been
d. Lewis antibodies usually occur without known antigenic stimulus in Le(a-b-)
individuals. Anti-Lea and anti-Leb may occur separately or together in the same serum,
virtually always as IgM molecules; they are capable of fixing complement, but not
crossing the placenta.
e. Most examples of anti-Leb react best with 0 and A2 red blood cells and are
designated anti-LebH. Those examples which react equally well with cells of all ABO
phenotypes that are Le(b+) are classified as anti-LebL. The latter antibodies are not
neutralized by saliva from 0 Le(a-b-) secretors, whereas the former are.
f. Serum containing both anti-Lea and -Leb activity often react with cord cells.
As cord cells do not usually react with anti-Lea or -Leb separately, it has been suggested
that this reaction is detecting a determinant other than Lea or Leb, called Lex.
g. As shown in Table 2-15, most Lewis antibodies agglutinate saline-suspended
red blood cells; however, the agglutination is often fragile and easily broken up if the
button of red blood cells is not re-suspended very gently following centrifugation.
Albumin does not usually enhance agglutination by Lewis antibodies. Many of these
antibodies react at 37C by the antiglobulin test. They are almost always IgM
complement-binding antibodies and are not detected if complement is absent from the
incubation mixture or if the antiglobulin serum has poor anti-complement activity.
Table 2-15. Serologic behavior of Lewis system antibodies.