Regulacion De La Respuesta Inmune

Available online at www.sciencedirect.com

Cellular Immunology 248 (2007) 12–17 www.elsevier.com/locate/ycimm

T cell recognition and immunity in the fetus and mother
Cody A. Koch
a

a,b

, Jeffrey L. Platt

a,b,c,d,*

Transplantation Biology Program, Mayo Clinic College of Medicine, Medical Sciences Building 2-66, 200 1st St SW, Rochester, MN 55905, USA b Department of Immunology,Mayo Clinic College of Medicine, Rochester, MN 55905, USA c Department of Surgery, Mayo Clinic College of Medicine, Rochester, MN 55905, USA d Department of Pediatrics, Mayo Clinic College of Medicine, Rochester, MN 55905, USA Received 20 December 2006; accepted 28 May 2007 Available online 24 October 2007

Abstract All multi-cellular organisms protect themselves from invasion by allogeneicorganisms and cells by mounting immune responses. While protective, allogeneic immune responses present a threat to successful reproduction in eutherian mammals in which the maternal immune system is exposed to the semi-allogeneic fetus. Thus, successful reproduction in eutherian mammals depends on mechanisms that control the potentially hostile maternal immune system without hindering immune responsesto potentially deadly infectious organisms. Three general mechanisms have been proposed to explain successful reproduction in mammals: (i) the formation of an anatomical barrier between mother and fetus; (ii) expression of allogeneic antigens at a very low level by the fetus; and (iii) hindrance of the maternal immune system responding to fetal antigens. These mechanisms explain in part how thefetus evades the maternal immune system; however, they do not explain fully the survival of the fetus. We hypothesize that site-specific immune suppression may play an important role in successful eutherian reproduction in conjunction with other mechanisms. Site-specific immune suppression at the fetal–maternal interface would protect the fetus while allowing peripheral maternal immune responses tocontinue unabated. Ó 2007 Elsevier Inc. All rights reserved.
Keywords: Anergy; Tolerance; Fetus; Pregnancy; Non-classical MHC; Chimerism; Tryptophan; Indoleamine 2,3-diosygenase

1. Introduction The immune system allows multi-cellular organisms to differentiate self and non-self, preventing parasitism by foreign cells and defending against infectious organisms. While one might envision thathighly disparate, xenogeneic, cells are easily recognized and destroyed by the host immune system, allogeneic and semi-allogeneic cells which closely resemble the host might be more difficult to recognize and destroy. However, all multi-cellular organisms mount rigorous allograft reactions. Allograft reactions may incidentally cross react with reactions against microorganisms. However, allograftreactions provide distinct advantages. Thus, allograft reactions pro* Corresponding author. Address: Transplantation Biology Program, Mayo Clinic College of Medicine, Medical Sciences Building 2-66, 200 1st St SW, Rochester, MN 55905, USA. Fax: +1 507 284 4957. E-mail address: platt.jeffrey@mayo.edu (J.L. Platt).

tect against invasion and expansion of allogeneic cells. Such invasion clearly threatenscolonial organisms; yet such invasion of allogeneic cells could also threaten motile animals [1]. In any case the powerful allogeneic response would seem to be a potential barrier to pregnancy yet, it is not. Here we discuss the mechanisms and how the barrier posed by alloimmunity may be overcome in pregnancy.

2. Fetal evasion of the immune system during pregnancy The overwhelming success of thefetus in evading immune rejection by the mother has puzzled investigators for decades. Medawar [2] proposed three general mechanisms for such evasion. First, the maternal immune system might not be capable of responding to fetal antigens due to mechanisms that induce anergy or tolerance in responding maternal cells. Second, an anatomical barrier might form between mother and fetus preventing...