The expanding field of psycho-neuro-immunology (PNI) has markedly increased the knowledge about the interference between the central nervous system and the immune system. PNI has shown that the activity of the immune system is influenced by the CNS and vice versa. The delicate health during chronic stress or the depression-like sickness behaviour during an acute infection like a flu are well known examples for the bilateral influences of the IS and the CNS. Moreover, the effects of antipsychotic drugs and antidepressants on the immune system, as well as the effect of immunomodulators on psychopathology are clinically important actions. The impact of the PNI network for psychiatry is obvious. Current Immunopsychiatry is searching for immunological mechanisms involved in the pathophysiology of psychiatric and neuro-psychiatric disorders.

Schizophrenia One third of schizophrenic patients show immunological abnormalities such as high antibody titers against several antigens (e.g.: Schwarz et al., 1999), or a distinct cytokine profile in serum and cerebrospinal fluid (CSF) (Müller et al., 1999a). This cytokine pattern seems to be 'Th2-like' ('Th2' describes one of two balanced arms of the specific immune system, responsible for either cell-mediated (Th1) or antibody-mediated (Th2) immune response). The immunological abnormalities seem to be associated with a younger age at onset, a preponderance of negative symptoms and therapy resistance to classical antipsychotic drugs. Molecular genetic data suggest a possible role of endogenous retroviruses in the ethiopathology of schizophrenia (Yolken et al., 2000). Some studies show distinct changes in the cytokine patterns and an activation of the cellular arm of the immune system after administration of atypical antipsychotics, indicating not only the neurochemical, but also a immunological potency of antipsychotics (Pollmacher et al., 1996; Müller et al., 1997; Müller et al., 1999b).

Depression Some studies indicate a Th1-like immune response in depressed patients (Maes, 1995). This is in contrast to the immunological findings in schizophrenia. Moreover, this kind of immune activation is similar to that seen under psychological stress (Leonard and Song, 1996), indicating a possible causative role of the stress, patients are suffering from. Antidepressants induce a shift from Th1-like to Th2-like cytokine production of the treated immune cells in vitro (Maes et al., 1999).

Alzheimer's disease (AD) An activation of the microglia cells - the resident monocytes/macrophages in the brain parenchyma - in the surrounding of amyloid plaques was already described by Alois Alzheimer. The activated microglia cells are producing neurotoxic agents that worsen the neuronal degeneration induced by the amyloid plaques (Akiyama et al., 2000). On the other hand, it has been demonstrated that microglia is able to reduce the plaques after vaccination with amyloid beta (Schenk et al., 1999). Altogether, the immune response seems to play a crucial role in both, the pathophysiology and the treatment strategies of AD.

Obsessive-compulsive disorder and tics Autoimmune mechanisms seem to be associated with tics and obsessive-compulsive disorder (OCD). The 'pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections' (PANDAS) is a group of disorders of this category (Swedo et al., 1998). Elevated antibody titers against streptococci indicating an autoimmune reaction against bacteria are also reported in Gilles de la Tourette's syndrome (GTS) (Muller et al., 2000a; Muller et al., 2000b). Immunomodulatory therapies such as immunoglobulins and antibiotics are now in clinical trial as therapeutic aproaches of these disorders.

The expanding field of psycho-neuro-immunology has markedly increased the knowledge about the interference of the central nervous system and the immune system. Immunological abnormalities in psychiatric patients have been repeatedly described during the last decades. Modern concepts of immunology and the growing knowledge of psychoneuroimmunology (PNI) may help to understand the immunological mechanisms and to identify subgroups with distinct etiopathology in the heterogeneous psychiatric disorders.

September 30 to October 2, 2003 in Munich, Germany:'German Endocrine Brain Immune Network' (GEBIN) : international meeting on recent advances in the field of psychoneuroimmunology.   

Year 2000: Symposium on Immunology and Psychiatry: Research Strategies in Immunopsychiatry: Possible Targets for New Treatments