Discrimination of self from nonself is the major function of the immune system and
understanding the mechanism(s) involved a main employer of immunologists. Hence the age-old
puzzle of why a fetus that contains a panel of major histocompatibility (MHC) antigens derived
from its mother and its father is not rejected (spontaneously aborted) by lymphocytes from its
mother who should theoretically recognize foreign MHC molecules from the father has remained of
great interest. This dilemma has enticed immunologists and developmental biologists for many
years. This volume was created to present the information currently on hand in this subject to
the scientific public. The guest editor Professor Lars Olding has a long and distinguished
history of contributions in this field having been one of the main propo nents of the argument
that lymphocytes from the fetus play an active role in this process by suppressing lymphocytes
from the mother from proliferating and thereby acting as killer cells. His work has defined the
phenomenon and identified suppressor molecules (factors) involved in the process. In a
different but related chapter Margareta Unander extends such observations to the clinical
study of women with repeated habitual mIS carriages.
