Perspectives on the In Vivo Location of Cellular Interactions in the Humoral Immune Response

INTRODUCTION 440 HISTOLOGICAL DESCRIPTION 440 Cells 0/ the Lymphoid System ' 440 Reticular Cells 440 Macrophages 440 Endothelial cells ...... ..... ..... 441 Lymphocytes ........ 441 Lymphoblasts ........ 442 Plasma cells 442 Spleen ....... .. ........ 442 Lymph Nodes .... 443 Gutand Bronchial-Associated Lymphoid Tissue 444 LYMPHOCYTE SUBPOPULATIONS 444 Distribution in Tissues .. ... 444 Migration Patterns .. ... 446 LOCALIZATION OF THE HUMORAL IMMUNE RESPONSE ... .. . .. ..... 447 Lymphoid Tissue Changes 447 Formation a/ Germinal Centers .. 447 Antigen 449 Antibody and Antibody-Secreting Cells .. 451 Evidence for Cellular Interactions 452 CONCLUSIONS 453