Safety and Tolerability of XmAb®7195 in Adult Healthy Volunteers and Adult Subjects With a History of Allergic Rhinitis and/or Allergic Conjunctivitis and/or Atopic Dermatitis

Inclusion Criteria: * Adult males and females 18 to 50 years of age * Parts 1 and 3: Healthy subjects with no clinically significant abnormality identified on medical or laboratory evaluation and no history of any clinically significant disorder, condition, or disease that would pose a risk to subject safety or interfere with the study evaluation, procedures, or completion; * Part 2: Otherwise healthy male and female subjects with a history of allergic rhinitis and/or allergic conjunctivitis and/or atopic dermatitis with an elevated serum IgE * Subjects who are able and willing to give written informed consent; * Subjects who have the ability to complete all study assessments; * Subjects who are willing to forego other forms of experimental treatment during the study. Exclusion Criteria: * Subjects who have a clinically relevant history or presence of respiratory, gastrointestinal, renal, hepatic, hematological, lymphatic, neurological, cardiovascular, psychiatric, musculoskeletal, genitourinary, immunological, dermatological, connective tissue diseases, or disorders (other than allergic rhinitis and/or conjunctivitis and/or atopic dermatitis in Part 2) that would pose a significant risk to subject safety or significantly interfere with the study evaluation, procedures, or completion * Subjects who are positive for hepatitis B surface antigen (HBsAg), hepatitis C virus (HCV) antibody and/or human immunodeficiency virus (HIV) Type I or Type II tests at Screening; * Subjects who do not agree to use medically acceptable methods of contraception (as defined in the protocol); * Subject is pregnant or breast feeding, or planning to become pregnant within 3 months of administration of XmAb7195; * Subjects who have used any investigational drug in any clinical trial within 8 weeks prior to admission (Day -1), or have used an experimental monoclonal antibody; * Subjects with prior exposure to a monoclonal antibody; * Subjects with a history of anaphylaxis; * Subjects who have received live vaccines ≤ 3 months from Screening;