Even though diffusion chamber culture was commenced long before ortho dox tissue culture by Metchnikoff (1887) there have been only sporadic attempts to use this methodology to study cell proliferation (review by Carsten, Chap. 1). Not so long ago diffusion chamber culture was nicknamed "confusion chamber" culture. I believe this conference has removed the confusion and will truly point out the intrinsic value of the system. It is not a substitute for established in vitro culture nor for in vivo studies. It complements both. Dr. Arne B~yum introduced diffusion chamber culture at Brookhaven National Laboratory. After some modest success in showing that one could culture human bone marrow and with appropriate stimuli induce erythro poiesis in diffusion chambers, several of the participants at this conference visited Brookhaven to learn firsthand this simple technology and to apply it in their own laboratories. However, the technique did not spread widely and controversy arose in which the same question was repeatedly asked: Can the diffusion chamber technique provide information that is not ob tainable more rapidly and easily, and at less expense by the in vitro tech niques? As a result of our deep interest in and involvement with diffusion chamber culture Dr. A. L. Carsten and I organized this conference. A major objective of this conference was to seek answers to the above question.

I. Characterization of Progenitor Cells in Diffusion Chambers

1. History and Overview of the In Vivo Diffusion Chamber (DC) Culture System
2. Roles of CFU-S and CFU-C in Maintaining Cell Growth in Diffusion Chamber Cultures of Murine Marrow
3. Different Classes of Granulocyte Progenitor Cells Expressed in In Vivo Plasma Clot Diffusion Chamber Cultures
4. Human Granulopoietic Progenitor Cell Diversity and Regulation Studied in Diffusion Chambers
5. Studies on the Regulation of Diffusion Chamber Granulopoiesis
6. Megakaryocyte Growth in In Vitro Cultures and in Diffusion Chambers
II. Regulatory Mechanisms in Diffusion Chamber Cell Growth
1. Culture of Normal Human Blood Cells in a Diffusion Chamber System II. Lymphocyte and Plasma Cell Kinetics
2. Marrow Culture in Diffusion Chambers in Rabbits IV. Effects of Leukocyte Products on Granulopoiesis
3. Host-Mediated Regulatory Activities as Measured on Bone Marrow Cells Cultured in Diffusion Chambers and In Vitro
4. Growth of Canine Bone Marrow and Peripheral Blood Mononuclear Cells in In Vivo Plasma Clot Diffusion Chambers in Mice: Cytopoietic Activity, GM-CFC Content, and Physical Separation
5. Normal and Leukemic Hematopoiesis in Diffusion Chambers: Comparison with In Vitro Culture Systems
6. Stimulating Factor(s) of Hematopoiesis in the Bone Marrow of Mice Administered Hydroxyurea. Effects on Diffusion Chamber Progenitor Cells (DCPC) and on Pluripotent Stem Cells (CFU-S)
III. Cell Interactions, Cytogenetics, and Methodology
1. Use of Diffusion Chambers for Studying Cell Interactions: Sequential Sttudies of Eosinophil Granulocytopoiesis In Vivo
2. An Evaluation of Host Cell Contact in the Regulation of Diffusion Chamber Hematopoiesis
3. Stem Cells in Human Peripheral Blood: A Method for Histologic Analysis of Colony Formation in Plasma Clot Diffusion Chambers
4. The Growth of Colonies of Human Bone Marrow and Tumour Cells in Soft Agar in Diffusion Chambers
5. Diffusion Chamber Cultures for Mutagenic and Carcinogenic Assays
IV. Characterization of Tumour and Leukemic Cell Growth
1. A Colony-Forming Assay for Experimental Tumours Using the Plasma Clot Diffusion Chamber
2. Long-Term Culture of Monoclonal Human Tumour Cells in Diffusion Chambers
3. The Use of Diffusion Chambers in the Study of Tumour Immunobiology and Lymphokines
4. Differentiation into Granulopoiesis in Human Acute Leukemia and Blast Crisis in Chronic Myelocytic Leukemia
5. Isolated Leukemic Cell Influence in Normal Hemic Colony Growth
V. Erythropoiesis in Plasma Clot Diffusion Chamber (PCDC) Culture
VI. Summary and Conclusions
List of Participants.